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 $181.39   11.179%   $201.6676   $201.67   $201.65   $201.70  
  Purchase #2 $219.36   12.515%   $246.8129   $246.81   $246.80   $246.80  
  Purchase #3 $203.35   10.408%   $224.5147   $224.51   $224.50   $224.50  
  Purchase #4 $192.32   10.545%   $212.6001   $212.60   $212.60   $212.60  
  Purchase #5 $41.70   3.141%   $43.0098   $43.01   $43.00   $43.00  
  Purchase #6 $213.91   12.424%   $240.4862   $240.49   $240.50   $240.50  
  Purchase #7 $7.31   11.217%   $8.13   $8.13   $8.15   $8.10  
  7 purchase totals = $1,059.34       $1,177.2213   $1,177.22   $1,177.20   $1,177.20