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	$35.27	4.236%	$36.764	$36.76	$36.75	$36.80
Purchase #2	$30.73	4.493%	$32.1107	$32.11	$32.10	$32.10
Purchase #3	$213.89	7.549%	$230.0366	$230.04	$230.05	$230.00
Purchase #4	$107.72	3.843%	$111.8597	$111.86	$111.85	$111.90
Purchase #5	$170.61	8.354%	$184.8628	$184.86	$184.85	$184.90
Purchase #6	$162.31	5.173%	$170.7063	$170.71	$170.70	$170.70
Purchase #7	$227.86	11.461%	$253.975	$253.98	$254.00	$254.00
7 purchase totals =	$948.39		$1,020.3151	$1,020.32	$1,020.30	$1,020.40