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	$88.72	7.667%	$95.5222	$95.52	$95.50	$95.50
Purchase #2	$33.91	6.317%	$36.0521	$36.05	$36.05	$36.10
Purchase #3	$139.85	7.197%	$149.915	$149.92	$149.90	$149.90
Purchase #4	$92.89	13.148%	$105.1032	$105.10	$105.10	$105.10
Purchase #5	$57.59	13.328%	$65.2656	$65.27	$65.25	$65.30
Purchase #6	$6.39	10.667%	$7.0716	$7.07	$7.05	$7.10
Purchase #7	$40.41	6.213%	$42.9207	$42.92	$42.90	$42.90
7 purchase totals =	$459.76		$501.8504	$501.85	$501.75	$501.90