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 $60.65   13.303%   $68.7183   $68.72   $68.70   $68.70  
  Purchase #2 $197.57   6.596%   $210.6017   $210.60   $210.60   $210.60  
  Purchase #3 $167.79   9.651%   $183.9834   $183.98   $184.00   $184.00  
  Purchase #4 $97.85   9.319%   $106.9686   $106.97   $106.95   $107.00  
  Purchase #5 $247.85   8.582%   $269.1205   $269.12   $269.10   $269.10  
  Purchase #6 $94.85   8.423%   $102.8392   $102.84   $102.85   $102.80  
  Purchase #7 $181.69   5.849%   $192.317   $192.32   $192.30   $192.30  
  7 purchase totals = $1,048.25       $1,134.5487   $1,134.55   $1,134.50   $1,134.50