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	$137.27	8.201%	$148.5275	$148.53	$148.55	$148.50
Purchase #2	$233.93	12.809%	$263.8941	$263.89	$263.90	$263.90
Purchase #3	$165.47	11.546%	$184.5752	$184.58	$184.60	$184.60
Purchase #4	$225.57	12.405%	$253.552	$253.55	$253.55	$253.60
Purchase #5	$167.25	3.519%	$173.1355	$173.14	$173.15	$173.10
Purchase #6	$101.44	6.165%	$107.6938	$107.69	$107.70	$107.70
Purchase #7	$83.56	8.339%	$90.5281	$90.53	$90.55	$90.50
7 purchase totals =	$1,114.49		$1,221.9062	$1,221.91	$1,222.00	$1,221.90