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 $65.86   9.305%   $71.9883   $71.99   $72.00   $72.00  
  Purchase #2 $220.54   3.496%   $228.2501   $228.25   $228.25   $228.30  
  Purchase #3 $179.59   13.623%   $204.0555   $204.06   $204.05   $204.10  
  Purchase #4 $147.79   8.676%   $160.6123   $160.61   $160.60   $160.60  
  Purchase #5 $182.61   11.823%   $204.2   $204.20   $204.20   $204.20  
  Purchase #6 $80.92   12.402%   $90.9557   $90.96   $90.95   $91.00  
  Purchase #7 $167.62   6.282%   $178.1499   $178.15   $178.15   $178.10  
  7 purchase totals = $1,044.93       $1,138.2118   $1,138.22   $1,138.20   $1,138.30