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	$133.72	9.273%	$146.1199	$146.12	$146.10	$146.10
Purchase #2	$20.63	13.539%	$23.4231	$23.42	$23.40	$23.40
Purchase #3	$204.80	4.413%	$213.8378	$213.84	$213.85	$213.80
Purchase #4	$182.74	4.401%	$190.7824	$190.78	$190.80	$190.80
Purchase #5	$102.87	8.468%	$111.581	$111.58	$111.60	$111.60
Purchase #6	$182.48	4.827%	$191.2883	$191.29	$191.30	$191.30
Purchase #7	$186.54	5.214%	$196.2662	$196.27	$196.25	$196.30
7 purchase totals =	$1,013.78		$1,073.2987	$1,073.30	$1,073.30	$1,073.30