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	$100.86	9.105%	$110.0433	$110.04	$110.05	$110.00
Purchase #2	$238.89	10.626%	$264.2745	$264.27	$264.25	$264.30
Purchase #3	$228.28	12.473%	$256.7534	$256.75	$256.75	$256.80
Purchase #4	$100.84	10.217%	$111.1428	$111.14	$111.15	$111.10
Purchase #5	$90.43	11.618%	$100.9362	$100.94	$100.95	$100.90
Purchase #6	$18.46	7.115%	$19.7734	$19.77	$19.75	$19.80
Purchase #7	$146.76	10.775%	$162.5734	$162.57	$162.55	$162.60
7 purchase totals =	$924.52		$1,025.4970	$1,025.48	$1,025.45	$1,025.50