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	$237.65	6.153%	$252.2726	$252.27	$252.25	$252.30
Purchase #2	$85.50	4.507%	$89.3535	$89.35	$89.35	$89.40
Purchase #3	$135.48	12.190%	$151.995	$152.00	$152.00	$152.00
Purchase #4	$187.85	6.845%	$200.7083	$200.71	$200.70	$200.70
Purchase #5	$21.37	12.433%	$24.0269	$24.03	$24.05	$24.00
Purchase #6	$162.61	7.573%	$174.9245	$174.92	$174.90	$174.90
Purchase #7	$222.27	3.536%	$230.1295	$230.13	$230.15	$230.10
7 purchase totals =	$1,052.73		$1,123.4103	$1,123.41	$1,123.40	$1,123.40