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 $151.48   10.270%   $167.037   $167.04   $167.05   $167.00  
  Purchase #2 $15.74   3.568%   $16.3016   $16.30   $16.30   $16.30  
  Purchase #3 $216.80   7.465%   $232.9841   $232.98   $233.00   $233.00  
  Purchase #4 $237.41   11.766%   $265.3437   $265.34   $265.35   $265.30  
  Purchase #5 $106.72   6.639%   $113.8051   $113.81   $113.80   $113.80  
  Purchase #6 $62.90   13.229%   $71.221   $71.22   $71.20   $71.20  
  Purchase #7 $184.67   9.231%   $201.7169   $201.72   $201.70   $201.70  
  7 purchase totals = $975.72       $1,068.4094   $1,068.41   $1,068.40   $1,068.30