Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $214.44   6.182%   $227.6967   $227.70   $227.70   $227.70  
  Purchase #2 $246.60   12.415%   $277.2154   $277.22   $277.20   $277.20  
  Purchase #3 $22.34   11.438%   $24.8952   $24.90   $24.90   $24.90  
  Purchase #4 $207.50   12.570%   $233.5828   $233.58   $233.60   $233.60  
  Purchase #5 $232.31   6.234%   $246.7922   $246.79   $246.80   $246.80  
  Purchase #6 $226.58   6.406%   $241.0947   $241.09   $241.10   $241.10  
  Purchase #7 $195.85   7.491%   $210.5211   $210.52   $210.50   $210.50  
  7 purchase totals = $1,345.62       $1,461.7981   $1,461.80   $1,461.80   $1,461.80