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	$20.55	9.261%	$22.4531	$22.45	$22.45	$22.50
Purchase #2	$53.51	10.721%	$59.2468	$59.25	$59.25	$59.20
Purchase #3	$29.48	9.853%	$32.3847	$32.38	$32.40	$32.40
Purchase #4	$102.72	3.864%	$106.6891	$106.69	$106.70	$106.70
Purchase #5	$173.62	9.570%	$190.2354	$190.24	$190.25	$190.20
Purchase #6	$153.94	3.348%	$159.0939	$159.09	$159.10	$159.10
Purchase #7	$61.95	4.133%	$64.5104	$64.51	$64.50	$64.50
7 purchase totals =	$595.77		$634.6134	$634.61	$634.65	$634.60