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	$175.97	13.781%	$200.2204	$200.22	$200.20	$200.20
Purchase #2	$172.29	10.675%	$190.682	$190.68	$190.70	$190.70
Purchase #3	$130.75	7.753%	$140.887	$140.89	$140.90	$140.90
Purchase #4	$28.83	5.856%	$30.5183	$30.52	$30.50	$30.50
Purchase #5	$166.82	11.122%	$185.3737	$185.37	$185.35	$185.40
Purchase #6	$182.39	7.813%	$196.6401	$196.64	$196.65	$196.60
Purchase #7	$226.71	10.829%	$251.2604	$251.26	$251.25	$251.30
7 purchase totals =	$1,083.76		$1,195.5819	$1,195.58	$1,195.55	$1,195.60