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	$152.82	8.517%	$165.8357	$165.84	$165.85	$165.80
Purchase #2	$41.74	13.770%	$47.4876	$47.49	$47.50	$47.50
Purchase #3	$24.70	9.496%	$27.0455	$27.05	$27.05	$27.00
Purchase #4	$232.86	11.719%	$260.1489	$260.15	$260.15	$260.10
Purchase #5	$238.65	10.841%	$264.522	$264.52	$264.50	$264.50
Purchase #6	$205.43	8.329%	$222.5403	$222.54	$222.55	$222.50
Purchase #7	$111.65	9.217%	$121.9408	$121.94	$121.95	$121.90
7 purchase totals =	$1,007.85		$1,109.5208	$1,109.53	$1,109.55	$1,109.30