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	$150.90	4.523%	$157.7252	$157.73	$157.75	$157.70
Purchase #2	$48.89	13.435%	$55.4584	$55.46	$55.45	$55.50
Purchase #3	$244.63	13.790%	$278.3645	$278.36	$278.35	$278.40
Purchase #4	$228.58	6.429%	$243.2754	$243.28	$243.30	$243.30
Purchase #5	$91.43	4.527%	$95.569	$95.57	$95.55	$95.60
Purchase #6	$76.69	12.672%	$86.4082	$86.41	$86.40	$86.40
Purchase #7	$222.78	8.580%	$241.8945	$241.89	$241.90	$241.90
7 purchase totals =	$1,063.90		$1,158.6952	$1,158.70	$1,158.70	$1,158.80