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	$118.71	7.429%	$127.529	$127.53	$127.55	$127.50
Purchase #2	$187.46	6.785%	$200.1792	$200.18	$200.20	$200.20
Purchase #3	$231.48	11.864%	$258.9428	$258.94	$258.95	$258.90
Purchase #4	$181.90	4.741%	$190.5239	$190.52	$190.50	$190.50
Purchase #5	$54.45	10.432%	$60.1302	$60.13	$60.15	$60.10
Purchase #6	$36.68	13.638%	$41.6824	$41.68	$41.70	$41.70
Purchase #7	$175.39	13.523%	$199.108	$199.11	$199.10	$199.10
7 purchase totals =	$986.07		$1,078.0955	$1,078.09	$1,078.15	$1,078.00