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	$157.57	13.447%	$178.7584	$178.76	$178.75	$178.80
Purchase #2	$33.70	13.733%	$38.328	$38.33	$38.35	$38.30
Purchase #3	$50.29	13.807%	$57.2335	$57.23	$57.25	$57.20
Purchase #4	$191.55	4.600%	$200.3613	$200.36	$200.35	$200.40
Purchase #5	$244.33	13.456%	$277.207	$277.21	$277.20	$277.20
Purchase #6	$135.85	3.819%	$141.0381	$141.04	$141.05	$141.00
Purchase #7	$138.77	11.614%	$154.8867	$154.89	$154.90	$154.90
7 purchase totals =	$952.06		$1,047.8130	$1,047.82	$1,047.85	$1,047.80