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	$9.43	7.455%	$10.133	$10.13	$10.15	$10.10
Purchase #2	$168.40	4.452%	$175.8972	$175.90	$175.90	$175.90
Purchase #3	$227.73	11.159%	$253.1424	$253.14	$253.15	$253.10
Purchase #4	$245.38	3.527%	$254.0346	$254.03	$254.05	$254.00
Purchase #5	$90.93	10.841%	$100.7877	$100.79	$100.80	$100.80
Purchase #6	$163.30	13.867%	$185.9448	$185.94	$185.95	$185.90
Purchase #7	$128.30	6.429%	$136.5484	$136.55	$136.55	$136.50
7 purchase totals =	$1,033.47		$1,116.4881	$1,116.48	$1,116.55	$1,116.30