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	$170.65	12.343%	$191.7133	$191.71	$191.70	$191.70
Purchase #2	$48.80	7.219%	$52.3229	$52.32	$52.30	$52.30
Purchase #3	$143.29	5.302%	$150.8872	$150.89	$150.90	$150.90
Purchase #4	$109.35	3.385%	$113.0515	$113.05	$113.05	$113.10
Purchase #5	$110.41	11.435%	$123.0354	$123.04	$123.05	$123.00
Purchase #6	$97.82	9.595%	$107.2058	$107.21	$107.20	$107.20
Purchase #7	$61.62	4.349%	$64.2999	$64.30	$64.30	$64.30
7 purchase totals =	$741.94		$802.5160	$802.52	$802.50	$802.50