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	$42.51	9.276%	$46.4532	$46.45	$46.45	$46.50
Purchase #2	$89.95	3.502%	$93.1	$93.10	$93.10	$93.10
Purchase #3	$12.89	5.251%	$13.5669	$13.57	$13.55	$13.60
Purchase #4	$175.93	4.629%	$184.0738	$184.07	$184.05	$184.10
Purchase #5	$106.31	9.476%	$116.3839	$116.38	$116.40	$116.40
Purchase #6	$64.59	10.537%	$71.3958	$71.40	$71.40	$71.40
Purchase #7	$179.65	9.360%	$196.4652	$196.47	$196.45	$196.50
7 purchase totals =	$671.83		$721.4388	$721.44	$721.40	$721.60