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	$171.95	6.376%	$182.9135	$182.91	$182.90	$182.90
Purchase #2	$33.48	4.278%	$34.9123	$34.91	$34.90	$34.90
Purchase #3	$208.72	6.593%	$222.4809	$222.48	$222.50	$222.50
Purchase #4	$52.62	3.236%	$54.3228	$54.32	$54.30	$54.30
Purchase #5	$130.31	9.267%	$142.3858	$142.39	$142.40	$142.40
Purchase #6	$51.43	5.284%	$54.1476	$54.15	$54.15	$54.10
Purchase #7	$230.40	10.626%	$254.8823	$254.88	$254.90	$254.90
7 purchase totals =	$878.91		$946.0452	$946.04	$946.05	$946.00