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	$176.57	7.821%	$190.3795	$190.38	$190.40	$190.40
Purchase #2	$132.57	7.660%	$142.7249	$142.72	$142.70	$142.70
Purchase #3	$145.67	9.439%	$159.4198	$159.42	$159.40	$159.40
Purchase #4	$171.82	13.551%	$195.1033	$195.10	$195.10	$195.10
Purchase #5	$34.80	9.672%	$38.1659	$38.17	$38.15	$38.20
Purchase #6	$91.89	3.190%	$94.8213	$94.82	$94.80	$94.80
Purchase #7	$222.40	11.201%	$247.311	$247.31	$247.30	$247.30
7 purchase totals =	$975.72		$1,067.9257	$1,067.92	$1,067.85	$1,067.90