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	$247.83	12.361%	$278.4643	$278.46	$278.45	$278.50
Purchase #2	$238.74	7.548%	$256.7601	$256.76	$256.75	$256.80
Purchase #3	$64.76	11.860%	$72.4405	$72.44	$72.45	$72.40
Purchase #4	$191.66	8.759%	$208.4475	$208.45	$208.45	$208.40
Purchase #5	$74.34	11.700%	$83.0378	$83.04	$83.05	$83.00
Purchase #6	$72.61	6.751%	$77.5119	$77.51	$77.50	$77.50
Purchase #7	$203.31	4.423%	$212.3024	$212.30	$212.30	$212.30
7 purchase totals =	$1,093.25		$1,188.9645	$1,188.96	$1,188.95	$1,188.90