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	$163.86	12.198%	$183.8476	$183.85	$183.85	$183.80
Purchase #2	$144.56	4.869%	$151.5986	$151.60	$151.60	$151.60
Purchase #3	$69.53	3.408%	$71.8996	$71.90	$71.90	$71.90
Purchase #4	$43.80	3.647%	$45.3974	$45.40	$45.40	$45.40
Purchase #5	$120.53	10.581%	$133.2833	$133.28	$133.30	$133.30
Purchase #6	$59.84	9.454%	$65.4973	$65.50	$65.50	$65.50
Purchase #7	$195.61	10.400%	$215.9534	$215.95	$215.95	$216.00
7 purchase totals =	$797.73		$867.4772	$867.48	$867.50	$867.50