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	$51.44	3.586%	$53.2846	$53.28	$53.30	$53.30
Purchase #2	$182.98	5.706%	$193.4208	$193.42	$193.40	$193.40
Purchase #3	$83.83	10.422%	$92.5668	$92.57	$92.55	$92.60
Purchase #4	$45.86	5.388%	$48.3309	$48.33	$48.35	$48.30
Purchase #5	$36.86	5.291%	$38.8103	$38.81	$38.80	$38.80
Purchase #6	$172.68	7.502%	$185.6345	$185.63	$185.65	$185.60
Purchase #7	$143.27	5.292%	$150.8518	$150.85	$150.85	$150.90
7 purchase totals =	$716.92		$762.8997	$762.89	$762.90	$762.90