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	$229.76	7.767%	$247.6055	$247.61	$247.60	$247.60
Purchase #2	$239.72	4.345%	$250.1358	$250.14	$250.15	$250.10
Purchase #3	$154.37	3.757%	$160.1697	$160.17	$160.15	$160.20
Purchase #4	$77.64	7.790%	$83.6882	$83.69	$83.70	$83.70
Purchase #5	$6.27	8.368%	$6.7947	$6.79	$6.80	$6.80
Purchase #6	$38.98	11.157%	$43.329	$43.33	$43.35	$43.30
Purchase #7	$64.30	13.173%	$72.7702	$72.77	$72.75	$72.80
7 purchase totals =	$811.04		$864.4931	$864.50	$864.50	$864.50