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	$59.67	8.809%	$64.9263	$64.93	$64.95	$64.90
Purchase #2	$161.67	12.848%	$182.4414	$182.44	$182.45	$182.40
Purchase #3	$85.82	11.495%	$95.685	$95.69	$95.70	$95.70
Purchase #4	$193.93	4.615%	$202.8799	$202.88	$202.90	$202.90
Purchase #5	$155.68	10.644%	$172.2506	$172.25	$172.25	$172.30
Purchase #6	$162.44	6.789%	$173.4681	$173.47	$173.45	$173.50
Purchase #7	$223.67	3.641%	$231.8138	$231.81	$231.80	$231.80
7 purchase totals =	$1,042.88		$1,123.4651	$1,123.47	$1,123.50	$1,123.50