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	$69.54	9.162%	$75.9113	$75.91	$75.90	$75.90
Purchase #2	$133.90	8.323%	$145.0445	$145.04	$145.05	$145.00
Purchase #3	$190.48	3.296%	$196.7582	$196.76	$196.75	$196.80
Purchase #4	$203.86	4.269%	$212.5628	$212.56	$212.55	$212.60
Purchase #5	$180.43	11.125%	$200.5028	$200.50	$200.50	$200.50
Purchase #6	$100.37	5.146%	$105.535	$105.54	$105.55	$105.50
Purchase #7	$37.68	7.607%	$40.5463	$40.55	$40.55	$40.50
7 purchase totals =	$916.26		$976.8609	$976.86	$976.85	$976.80