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 $54.84   12.429%   $61.6561   $61.66   $61.65   $61.70  
  Purchase #2 $211.58   3.179%   $218.3061   $218.31   $218.30   $218.30  
  Purchase #3 $60.37   13.219%   $68.3503   $68.35   $68.35   $68.40  
  Purchase #4 $49.51   7.849%   $53.396   $53.40   $53.40   $53.40  
  Purchase #5 $154.88   11.597%   $172.8414   $172.84   $172.85   $172.80  
  Purchase #6 $146.90   13.714%   $167.0459   $167.05   $167.05   $167.00  
  Purchase #7 $197.81   7.670%   $212.982   $212.98   $213.00   $213.00  
  7 purchase totals = $875.89       $954.5778   $954.59   $954.60   $954.60