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	$173.68	9.737%	$190.5912	$190.59	$190.60	$190.60
Purchase #2	$194.86	7.698%	$209.8603	$209.86	$209.85	$209.90
Purchase #3	$241.43	3.598%	$250.1167	$250.12	$250.10	$250.10
Purchase #4	$150.60	7.223%	$161.4778	$161.48	$161.50	$161.50
Purchase #5	$78.88	4.130%	$82.1377	$82.14	$82.15	$82.10
Purchase #6	$88.77	5.123%	$93.3177	$93.32	$93.30	$93.30
Purchase #7	$196.86	12.282%	$221.0383	$221.04	$221.05	$221.00
7 purchase totals =	$1,125.08		$1,208.5397	$1,208.55	$1,208.55	$1,208.50