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	$52.91	13.160%	$59.873	$59.87	$59.85	$59.90
Purchase #2	$97.47	13.504%	$110.6323	$110.63	$110.65	$110.60
Purchase #3	$98.73	7.484%	$106.119	$106.12	$106.10	$106.10
Purchase #4	$233.78	8.315%	$253.2188	$253.22	$253.20	$253.20
Purchase #5	$189.34	12.386%	$212.7917	$212.79	$212.80	$212.80
Purchase #6	$162.58	6.774%	$173.5932	$173.59	$173.60	$173.60
Purchase #7	$101.34	10.373%	$111.852	$111.85	$111.85	$111.90
7 purchase totals =	$936.15		$1,028.0800	$1,028.07	$1,028.05	$1,028.10