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 $176.26   10.799%   $195.2943   $195.29   $195.30   $195.30  
  Purchase #2 $122.95   11.783%   $137.4372   $137.44   $137.45   $137.40  
  Purchase #3 $213.44   8.674%   $231.9538   $231.95   $231.95   $232.00  
  Purchase #4 $144.28   3.506%   $149.3385   $149.34   $149.35   $149.30  
  Purchase #5 $226.62   6.476%   $241.2959   $241.30   $241.30   $241.30  
  Purchase #6 $165.35   10.661%   $182.978   $182.98   $183.00   $183.00  
  Purchase #7 $9.50   10.542%   $10.5015   $10.50   $10.50   $10.50  
  7 purchase totals = $1,058.40       $1,148.7992   $1,148.80   $1,148.85   $1,148.80