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 $213.64   5.677%   $225.7683   $225.77   $225.75   $225.80  
  Purchase #2 $195.38   8.232%   $211.4637   $211.46   $211.45   $211.50  
  Purchase #3 $122.50   6.606%   $130.5924   $130.59   $130.60   $130.60  
  Purchase #4 $26.93   13.428%   $30.5462   $30.55   $30.55   $30.50  
  Purchase #5 $172.92   9.614%   $189.5445   $189.54   $189.55   $189.50  
  Purchase #6 $148.26   3.599%   $153.5959   $153.60   $153.60   $153.60  
  Purchase #7 $184.62   4.424%   $192.7876   $192.79   $192.80   $192.80  
  7 purchase totals = $1,064.25       $1,134.2986   $1,134.30   $1,134.30   $1,134.30