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 $160.52   9.746%   $176.1643   $176.16   $176.15   $176.20  
  Purchase #2 $74.89   10.412%   $82.6875   $82.69   $82.70   $82.70  
  Purchase #3 $94.85   12.171%   $106.3942   $106.39   $106.40   $106.40  
  Purchase #4 $180.65   7.154%   $193.5737   $193.57   $193.55   $193.60  
  Purchase #5 $54.99   7.700%   $59.2242   $59.22   $59.20   $59.20  
  Purchase #6 $172.77   5.604%   $182.452   $182.45   $182.45   $182.50  
  Purchase #7 $193.65   8.778%   $210.6486   $210.65   $210.65   $210.60  
  7 purchase totals = $932.32       $1,011.1445   $1,011.13   $1,011.10   $1,011.20