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	$125.78	3.553%	$130.249	$130.25	$130.25	$130.20
Purchase #2	$81.90	9.114%	$89.3644	$89.36	$89.35	$89.40
Purchase #3	$141.75	8.456%	$153.7364	$153.74	$153.75	$153.70
Purchase #4	$35.37	13.818%	$40.2574	$40.26	$40.25	$40.30
Purchase #5	$35.65	10.869%	$39.5248	$39.52	$39.50	$39.50
Purchase #6	$20.31	8.860%	$22.1095	$22.11	$22.10	$22.10
Purchase #7	$202.78	9.776%	$222.6038	$222.60	$222.60	$222.60
7 purchase totals =	$643.54		$697.8453	$697.84	$697.80	$697.80