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	$40.48	7.500%	$43.516	$43.52	$43.50	$43.50
Purchase #2	$59.74	11.757%	$66.7636	$66.76	$66.75	$66.80
Purchase #3	$242.27	13.808%	$275.7226	$275.72	$275.70	$275.70
Purchase #4	$179.32	12.605%	$201.9233	$201.92	$201.90	$201.90
Purchase #5	$246.72	10.233%	$271.9669	$271.97	$271.95	$272.00
Purchase #6	$169.36	12.746%	$190.9466	$190.95	$190.95	$190.90
Purchase #7	$28.39	3.558%	$29.4001	$29.40	$29.40	$29.40
7 purchase totals =	$966.28		$1,080.2391	$1,080.24	$1,080.15	$1,080.20