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	$59.30	13.348%	$67.2154	$67.22	$67.20	$67.20
Purchase #2	$168.27	6.655%	$179.4684	$179.47	$179.45	$179.50
Purchase #3	$228.58	8.329%	$247.6184	$247.62	$247.60	$247.60
Purchase #4	$28.47	12.564%	$32.047	$32.05	$32.05	$32.00
Purchase #5	$133.33	9.186%	$145.5777	$145.58	$145.60	$145.60
Purchase #6	$28.90	9.590%	$31.6715	$31.67	$31.65	$31.70
Purchase #7	$37.41	12.570%	$42.1124	$42.11	$42.10	$42.10
7 purchase totals =	$684.26		$745.7108	$745.72	$745.65	$745.70