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	$59.55	9.437%	$65.1697	$65.17	$65.15	$65.20
Purchase #2	$56.45	11.450%	$62.9135	$62.91	$62.90	$62.90
Purchase #3	$140.47	12.221%	$157.6368	$157.64	$157.65	$157.60
Purchase #4	$139.35	7.745%	$150.1427	$150.14	$150.15	$150.10
Purchase #5	$49.35	6.383%	$52.5	$52.50	$52.50	$52.50
Purchase #6	$227.99	11.675%	$254.6078	$254.61	$254.60	$254.60
Purchase #7	$233.25	13.311%	$264.2979	$264.30	$264.30	$264.30
7 purchase totals =	$906.41		$1,007.2684	$1,007.27	$1,007.25	$1,007.20