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	$78.51	11.741%	$87.7279	$87.73	$87.75	$87.70
Purchase #2	$67.29	6.791%	$71.8597	$71.86	$71.85	$71.90
Purchase #3	$21.29	3.760%	$22.0905	$22.09	$22.10	$22.10
Purchase #4	$196.62	10.153%	$216.5828	$216.58	$216.60	$216.60
Purchase #5	$27.81	4.298%	$29.0053	$29.01	$29.00	$29.00
Purchase #6	$81.65	9.626%	$89.5096	$89.51	$89.50	$89.50
Purchase #7	$110.60	8.869%	$120.4091	$120.41	$120.40	$120.40
7 purchase totals =	$583.77		$637.1849	$637.19	$637.20	$637.20