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 $49.50   5.398%   $52.172   $52.17   $52.15   $52.20  
  Purchase #2 $228.37   5.694%   $241.3734   $241.37   $241.35   $241.40  
  Purchase #3 $198.34   10.401%   $218.9693   $218.97   $218.95   $219.00  
  Purchase #4 $37.97   7.629%   $40.8667   $40.87   $40.85   $40.90  
  Purchase #5 $211.90   7.155%   $227.0614   $227.06   $227.05   $227.10  
  Purchase #6 $171.58   9.814%   $188.4189   $188.42   $188.40   $188.40  
  Purchase #7 $56.27   12.395%   $63.2447   $63.24   $63.25   $63.20  
  7 purchase totals = $953.93       $1,032.1064   $1,032.10   $1,032.00   $1,032.20