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	$216.43	13.834%	$246.3709	$246.37	$246.35	$246.40
Purchase #2	$187.41	7.173%	$200.8529	$200.85	$200.85	$200.90
Purchase #3	$228.47	9.829%	$250.9263	$250.93	$250.95	$250.90
Purchase #4	$165.43	13.496%	$187.7564	$187.76	$187.75	$187.80
Purchase #5	$205.76	8.822%	$223.9121	$223.91	$223.90	$223.90
Purchase #6	$212.65	13.873%	$242.1509	$242.15	$242.15	$242.20
Purchase #7	$55.86	10.690%	$61.8314	$61.83	$61.85	$61.80
7 purchase totals =	$1,272.01		$1,413.8009	$1,413.80	$1,413.80	$1,413.90