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	$244.36	4.104%	$254.3885	$254.39	$254.40	$254.40
Purchase #2	$62.68	11.869%	$70.1195	$70.12	$70.10	$70.10
Purchase #3	$186.72	5.279%	$196.5769	$196.58	$196.60	$196.60
Purchase #4	$19.60	6.445%	$20.8632	$20.86	$20.85	$20.90
Purchase #5	$33.81	11.717%	$37.7715	$37.77	$37.75	$37.80
Purchase #6	$247.71	5.842%	$262.1812	$262.18	$262.20	$262.20
Purchase #7	$189.51	7.752%	$204.2008	$204.20	$204.20	$204.20
7 purchase totals =	$984.39		$1,046.1016	$1,046.10	$1,046.10	$1,046.20