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	$69.47	3.594%	$71.9668	$71.97	$71.95	$72.00
Purchase #2	$120.28	11.240%	$133.7995	$133.80	$133.80	$133.80
Purchase #3	$90.92	13.360%	$103.0669	$103.07	$103.05	$103.10
Purchase #4	$91.28	4.456%	$95.3474	$95.35	$95.35	$95.30
Purchase #5	$189.94	5.562%	$200.5045	$200.50	$200.50	$200.50
Purchase #6	$165.52	10.534%	$182.9559	$182.96	$182.95	$183.00
Purchase #7	$127.90	7.853%	$137.944	$137.94	$137.95	$137.90
7 purchase totals =	$855.31		$925.5850	$925.59	$925.55	$925.60