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	$105.56	10.496%	$116.6396	$116.64	$116.65	$116.60
Purchase #2	$239.76	6.218%	$254.6683	$254.67	$254.65	$254.70
Purchase #3	$65.45	8.261%	$70.8568	$70.86	$70.85	$70.90
Purchase #4	$99.62	4.531%	$104.1338	$104.13	$104.15	$104.10
Purchase #5	$168.62	10.155%	$185.7434	$185.74	$185.75	$185.70
Purchase #6	$182.94	11.822%	$204.5672	$204.57	$204.55	$204.60
Purchase #7	$166.95	4.862%	$175.0671	$175.07	$175.05	$175.10
7 purchase totals =	$1,028.90		$1,111.6762	$1,111.68	$1,111.65	$1,111.70