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	$173.43	13.372%	$196.6211	$196.62	$196.60	$196.60
Purchase #2	$65.45	9.221%	$71.4851	$71.49	$71.50	$71.50
Purchase #3	$8.97	6.280%	$9.5333	$9.53	$9.55	$9.50
Purchase #4	$33.75	7.274%	$36.205	$36.21	$36.20	$36.20
Purchase #5	$118.26	8.388%	$128.1796	$128.18	$128.20	$128.20
Purchase #6	$88.90	11.661%	$99.2666	$99.27	$99.25	$99.30
Purchase #7	$248.76	4.412%	$259.7353	$259.74	$259.75	$259.70
7 purchase totals =	$737.52		$801.0260	$801.04	$801.05	$801.00