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	$130.94	12.350%	$147.1111	$147.11	$147.10	$147.10
Purchase #2	$52.93	9.651%	$58.0383	$58.04	$58.05	$58.00
Purchase #3	$50.27	12.436%	$56.5216	$56.52	$56.50	$56.50
Purchase #4	$178.51	5.632%	$188.5637	$188.56	$188.55	$188.60
Purchase #5	$105.67	12.318%	$118.6864	$118.69	$118.70	$118.70
Purchase #6	$212.72	13.713%	$241.8903	$241.89	$241.90	$241.90
Purchase #7	$213.72	3.800%	$221.8414	$221.84	$221.85	$221.80
7 purchase totals =	$944.76		$1,032.6528	$1,032.65	$1,032.65	$1,032.60