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 $75.66   8.847%   $82.3536   $82.35   $82.35   $82.40  
  Purchase #2 $202.44   12.720%   $228.1904   $228.19   $228.20   $228.20  
  Purchase #3 $35.72   9.459%   $39.0988   $39.10   $39.10   $39.10  
  Purchase #4 $208.76   11.826%   $233.448   $233.45   $233.45   $233.40  
  Purchase #5 $242.91   4.581%   $254.0377   $254.04   $254.05   $254.00  
  Purchase #6 $96.94   9.565%   $106.2123   $106.21   $106.20   $106.20  
  Purchase #7 $150.74   11.253%   $167.7028   $167.70   $167.70   $167.70  
  7 purchase totals = $1,013.17       $1,111.0436   $1,111.04   $1,111.05   $1,111.00