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	$33.30	5.738%	$35.2108	$35.21	$35.20	$35.20
Purchase #2	$215.81	3.707%	$223.8101	$223.81	$223.80	$223.80
Purchase #3	$82.92	10.837%	$91.906	$91.91	$91.90	$91.90
Purchase #4	$238.32	11.453%	$265.6148	$265.61	$265.60	$265.60
Purchase #5	$47.62	6.595%	$50.7605	$50.76	$50.75	$50.80
Purchase #6	$153.34	8.685%	$166.6576	$166.66	$166.65	$166.70
Purchase #7	$157.59	13.105%	$178.2422	$178.24	$178.25	$178.20
7 purchase totals =	$928.90		$1,012.2020	$1,012.20	$1,012.15	$1,012.20