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	$64.84	3.348%	$67.0108	$67.01	$67.00	$67.00
Purchase #2	$188.90	11.870%	$211.3224	$211.32	$211.30	$211.30
Purchase #3	$144.87	7.481%	$155.7077	$155.71	$155.70	$155.70
Purchase #4	$241.32	5.463%	$254.5033	$254.50	$254.50	$254.50
Purchase #5	$17.75	4.857%	$18.6121	$18.61	$18.60	$18.60
Purchase #6	$187.46	11.214%	$208.4818	$208.48	$208.50	$208.50
Purchase #7	$159.55	8.388%	$172.9331	$172.93	$172.95	$172.90
7 purchase totals =	$1,004.69		$1,088.5712	$1,088.56	$1,088.55	$1,088.50