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	$223.51	10.517%	$247.0165	$247.02	$247.00	$247.00
Purchase #2	$32.30	11.229%	$35.927	$35.93	$35.95	$35.90
Purchase #3	$40.82	10.320%	$45.0326	$45.03	$45.05	$45.00
Purchase #4	$38.81	9.331%	$42.4314	$42.43	$42.45	$42.40
Purchase #5	$55.91	8.148%	$60.4655	$60.47	$60.45	$60.50
Purchase #6	$213.87	8.163%	$231.3282	$231.33	$231.35	$231.30
Purchase #7	$52.57	5.324%	$55.3688	$55.37	$55.35	$55.40
7 purchase totals =	$657.79		$717.5700	$717.58	$717.60	$717.50