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 $146.82   4.174%   $152.9483   $152.95   $152.95   $152.90  
  Purchase #2 $85.80   9.511%   $93.9604   $93.96   $93.95   $94.00  
  Purchase #3 $66.93   12.148%   $75.0607   $75.06   $75.05   $75.10  
  Purchase #4 $214.53   9.421%   $234.7409   $234.74   $234.75   $234.70  
  Purchase #5 $12.57   8.270%   $13.6095   $13.61   $13.60   $13.60  
  Purchase #6 $238.42   6.150%   $253.0828   $253.08   $253.10   $253.10  
  Purchase #7 $219.36   3.294%   $226.5857   $226.59   $226.60   $226.60  
  7 purchase totals = $984.43       $1,049.9883   $1,049.99   $1,050.00   $1,050.00