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	$93.41	6.765%	$99.7292	$99.73	$99.75	$99.70
Purchase #2	$223.61	13.620%	$254.0657	$254.07	$254.05	$254.10
Purchase #3	$126.70	3.862%	$131.5932	$131.59	$131.60	$131.60
Purchase #4	$91.83	9.720%	$100.7559	$100.76	$100.75	$100.80
Purchase #5	$97.54	4.468%	$101.8981	$101.90	$101.90	$101.90
Purchase #6	$41.52	7.746%	$44.7361	$44.74	$44.75	$44.70
Purchase #7	$231.64	5.715%	$244.8782	$244.88	$244.90	$244.90
7 purchase totals =	$906.25		$977.6564	$977.67	$977.70	$977.70