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 $216.50   8.527%   $234.961   $234.96   $234.95   $235.00  
  Purchase #2 $235.35   4.424%   $245.7619   $245.76   $245.75   $245.80  
  Purchase #3 $172.49   11.771%   $192.7938   $192.79   $192.80   $192.80  
  Purchase #4 $196.48   11.106%   $218.3011   $218.30   $218.30   $218.30  
  Purchase #5 $39.55   11.819%   $44.2244   $44.22   $44.20   $44.20  
  Purchase #6 $144.76   4.163%   $150.7864   $150.79   $150.80   $150.80  
  Purchase #7 $90.31   3.752%   $93.6984   $93.70   $93.70   $93.70  
  7 purchase totals = $1,095.44       $1,180.5270   $1,180.52   $1,180.50   $1,180.60