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	$180.42	8.715%	$196.1436	$196.14	$196.15	$196.10
Purchase #2	$165.55	13.805%	$188.4042	$188.40	$188.40	$188.40
Purchase #3	$135.75	4.440%	$141.7773	$141.78	$141.80	$141.80
Purchase #4	$33.78	13.211%	$38.2427	$38.24	$38.25	$38.20
Purchase #5	$233.68	7.482%	$251.1639	$251.16	$251.15	$251.20
Purchase #6	$88.77	10.655%	$98.2284	$98.23	$98.25	$98.20
Purchase #7	$59.67	4.622%	$62.4279	$62.43	$62.45	$62.40
7 purchase totals =	$897.62		$976.3880	$976.38	$976.45	$976.30