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	$186.32	9.492%	$204.0055	$204.01	$204.00	$204.00
Purchase #2	$123.69	12.550%	$139.2131	$139.21	$139.20	$139.20
Purchase #3	$136.59	10.785%	$151.3212	$151.32	$151.30	$151.30
Purchase #4	$141.42	4.534%	$147.832	$147.83	$147.85	$147.80
Purchase #5	$137.83	9.823%	$151.369	$151.37	$151.35	$151.40
Purchase #6	$216.57	5.623%	$228.7477	$228.75	$228.75	$228.70
Purchase #7	$145.61	8.537%	$158.0407	$158.04	$158.05	$158.00
7 purchase totals =	$1,088.03		$1,180.5292	$1,180.53	$1,180.50	$1,180.40