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	$44.79	11.681%	$50.0219	$50.02	$50.00	$50.00
Purchase #2	$79.89	11.430%	$89.0214	$89.02	$89.00	$89.00
Purchase #3	$151.85	13.312%	$172.0643	$172.06	$172.05	$172.10
Purchase #4	$131.62	5.274%	$138.5616	$138.56	$138.55	$138.60
Purchase #5	$63.85	10.222%	$70.3767	$70.38	$70.40	$70.40
Purchase #6	$223.83	11.565%	$249.7159	$249.72	$249.70	$249.70
Purchase #7	$158.58	10.643%	$175.4577	$175.46	$175.45	$175.50
7 purchase totals =	$854.41		$945.2195	$945.22	$945.15	$945.30