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	$49.52	10.699%	$54.8181	$54.82	$54.80	$54.80
Purchase #2	$93.79	6.383%	$99.7766	$99.78	$99.80	$99.80
Purchase #3	$153.78	12.350%	$172.7718	$172.77	$172.75	$172.80
Purchase #4	$244.26	13.593%	$277.4623	$277.46	$277.45	$277.50
Purchase #5	$138.77	13.172%	$157.0488	$157.05	$157.05	$157.00
Purchase #6	$188.79	8.578%	$204.9844	$204.98	$205.00	$205.00
Purchase #7	$39.66	9.633%	$43.4804	$43.48	$43.50	$43.50
7 purchase totals =	$908.57		$1,010.3424	$1,010.34	$1,010.35	$1,010.40