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	$71.41	8.262%	$77.3099	$77.31	$77.30	$77.30
Purchase #2	$70.57	11.202%	$78.4753	$78.48	$78.50	$78.50
Purchase #3	$245.62	6.550%	$261.7081	$261.71	$261.70	$261.70
Purchase #4	$159.56	7.853%	$172.0902	$172.09	$172.10	$172.10
Purchase #5	$113.43	7.754%	$122.2254	$122.23	$122.25	$122.20
Purchase #6	$187.63	10.468%	$207.2711	$207.27	$207.25	$207.30
Purchase #7	$154.47	11.453%	$172.1614	$172.16	$172.15	$172.20
7 purchase totals =	$1,002.69		$1,091.2414	$1,091.25	$1,091.25	$1,091.30