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	$115.82	9.240%	$126.5218	$126.52	$126.50	$126.50
Purchase #2	$50.45	11.817%	$56.4117	$56.41	$56.40	$56.40
Purchase #3	$99.48	12.228%	$111.6444	$111.64	$111.65	$111.60
Purchase #4	$142.89	6.356%	$151.9721	$151.97	$151.95	$152.00
Purchase #5	$168.89	12.831%	$190.5603	$190.56	$190.55	$190.60
Purchase #6	$223.68	4.401%	$233.5242	$233.52	$233.50	$233.50
Purchase #7	$99.47	9.471%	$108.8908	$108.89	$108.90	$108.90
7 purchase totals =	$900.68		$979.5253	$979.51	$979.45	$979.50