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	$53.82	7.434%	$57.821	$57.82	$57.80	$57.80
Purchase #2	$159.87	6.469%	$170.212	$170.21	$170.20	$170.20
Purchase #3	$141.66	7.144%	$151.7802	$151.78	$151.80	$151.80
Purchase #4	$133.74	7.700%	$144.038	$144.04	$144.05	$144.00
Purchase #5	$96.34	9.459%	$105.4528	$105.45	$105.45	$105.50
Purchase #6	$156.99	6.475%	$167.1551	$167.16	$167.15	$167.20
Purchase #7	$154.36	7.808%	$166.4124	$166.41	$166.40	$166.40
7 purchase totals =	$896.78		$962.8715	$962.87	$962.85	$962.90