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 $176.68   4.476%   $184.5882   $184.59   $184.60   $184.60  
  Purchase #2 $65.72   6.516%   $70.0023   $70.00   $70.00   $70.00  
  Purchase #3 $101.25   9.516%   $110.885   $110.89   $110.90   $110.90  
  Purchase #4 $230.31   10.184%   $253.7648   $253.76   $253.75   $253.80  
  Purchase #5 $179.28   12.647%   $201.9535   $201.95   $201.95   $202.00  
  Purchase #6 $192.36   6.558%   $204.975   $204.98   $205.00   $205.00  
  Purchase #7 $62.57   11.347%   $69.6698   $69.67   $69.65   $69.70  
  7 purchase totals = $1,008.17       $1,095.8386   $1,095.84   $1,095.85   $1,096.00