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	$208.59	10.572%	$230.6421	$230.64	$230.65	$230.60
Purchase #2	$87.62	12.367%	$98.456	$98.46	$98.45	$98.50
Purchase #3	$121.61	5.200%	$127.9337	$127.93	$127.95	$127.90
Purchase #4	$200.71	11.551%	$223.894	$223.89	$223.90	$223.90
Purchase #5	$160.71	10.804%	$178.0731	$178.07	$178.05	$178.10
Purchase #6	$184.50	13.573%	$209.5422	$209.54	$209.55	$209.50
Purchase #7	$114.37	8.632%	$124.2424	$124.24	$124.25	$124.20
7 purchase totals =	$1,078.11		$1,192.7835	$1,192.77	$1,192.80	$1,192.70