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	$146.79	9.138%	$160.2037	$160.20	$160.20	$160.20
Purchase #2	$176.95	13.302%	$200.4879	$200.49	$200.50	$200.50
Purchase #3	$241.56	11.470%	$269.2669	$269.27	$269.25	$269.30
Purchase #4	$11.78	6.434%	$12.5379	$12.54	$12.55	$12.50
Purchase #5	$37.62	4.813%	$39.4307	$39.43	$39.45	$39.40
Purchase #6	$7.64	3.349%	$7.8959	$7.90	$7.90	$7.90
Purchase #7	$247.77	5.629%	$261.717	$261.72	$261.70	$261.70
7 purchase totals =	$870.11		$951.5400	$951.55	$951.55	$951.50