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	$94.49	6.562%	$100.6904	$100.69	$100.70	$100.70
Purchase #2	$53.68	3.591%	$55.6076	$55.61	$55.60	$55.60
Purchase #3	$234.40	4.372%	$244.648	$244.65	$244.65	$244.60
Purchase #4	$93.88	7.218%	$100.6563	$100.66	$100.65	$100.70
Purchase #5	$124.47	13.331%	$141.0631	$141.06	$141.05	$141.10
Purchase #6	$85.58	4.821%	$89.7058	$89.71	$89.70	$89.70
Purchase #7	$13.74	11.457%	$15.3142	$15.31	$15.30	$15.30
7 purchase totals =	$700.24		$747.6854	$747.69	$747.65	$747.70