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	$43.25	5.847%	$45.7788	$45.78	$45.80	$45.80
Purchase #2	$127.80	7.652%	$137.5793	$137.58	$137.60	$137.60
Purchase #3	$58.53	11.204%	$65.0877	$65.09	$65.10	$65.10
Purchase #4	$93.81	7.255%	$100.6159	$100.62	$100.60	$100.60
Purchase #5	$99.77	8.516%	$108.2664	$108.27	$108.25	$108.30
Purchase #6	$57.44	8.833%	$62.5137	$62.51	$62.50	$62.50
Purchase #7	$221.41	5.512%	$233.6141	$233.61	$233.60	$233.60
7 purchase totals =	$702.01		$753.4559	$753.46	$753.45	$753.50