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	$225.59	12.160%	$253.0217	$253.02	$253.00	$253.00
Purchase #2	$43.58	6.210%	$46.2863	$46.29	$46.30	$46.30
Purchase #3	$210.76	6.562%	$224.5901	$224.59	$224.60	$224.60
Purchase #4	$74.75	12.268%	$83.9203	$83.92	$83.90	$83.90
Purchase #5	$150.77	10.226%	$166.1877	$166.19	$166.20	$166.20
Purchase #6	$111.89	13.656%	$127.1697	$127.17	$127.15	$127.20
Purchase #7	$59.48	7.521%	$63.9535	$63.95	$63.95	$64.00
7 purchase totals =	$876.82		$965.1293	$965.13	$965.10	$965.20