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 $176.35   11.577%   $196.766   $196.77   $196.75   $196.80  
  Purchase #2 $235.94   3.268%   $243.6505   $243.65   $243.65   $243.70  
  Purchase #3 $150.59   12.799%   $169.864   $169.86   $169.85   $169.90  
  Purchase #4 $225.59   11.861%   $252.3472   $252.35   $252.35   $252.30  
  Purchase #5 $19.60   12.778%   $22.1045   $22.10   $22.10   $22.10  
  Purchase #6 $101.56   3.323%   $104.9348   $104.93   $104.95   $104.90  
  Purchase #7 $241.31   4.135%   $251.2882   $251.29   $251.30   $251.30  
  7 purchase totals = $1,150.94       $1,240.9552   $1,240.95   $1,240.95   $1,241.00