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	$46.90	4.363%	$48.9462	$48.95	$48.95	$48.90
Purchase #2	$215.82	9.574%	$236.4826	$236.48	$236.50	$236.50
Purchase #3	$223.52	11.529%	$249.2896	$249.29	$249.30	$249.30
Purchase #4	$40.57	11.306%	$45.1568	$45.16	$45.15	$45.20
Purchase #5	$104.73	11.287%	$116.5509	$116.55	$116.55	$116.60
Purchase #6	$213.26	5.619%	$225.2431	$225.24	$225.25	$225.20
Purchase #7	$59.63	4.301%	$62.1947	$62.19	$62.20	$62.20
7 purchase totals =	$904.43		$983.8639	$983.86	$983.90	$983.90