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	$92.92	6.855%	$99.2897	$99.29	$99.30	$99.30
Purchase #2	$69.59	4.303%	$72.5845	$72.58	$72.60	$72.60
Purchase #3	$172.78	10.624%	$191.1361	$191.14	$191.15	$191.10
Purchase #4	$122.83	8.327%	$133.0581	$133.06	$133.05	$133.10
Purchase #5	$182.88	11.186%	$203.337	$203.34	$203.35	$203.30
Purchase #6	$47.73	8.514%	$51.7937	$51.79	$51.80	$51.80
Purchase #7	$177.93	6.851%	$190.12	$190.12	$190.10	$190.10
7 purchase totals =	$866.66		$941.3191	$941.32	$941.35	$941.30