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	$201.82	13.585%	$229.2372	$229.24	$229.25	$229.20
Purchase #2	$161.44	4.493%	$168.6935	$168.69	$168.70	$168.70
Purchase #3	$204.79	11.103%	$227.5278	$227.53	$227.55	$227.50
Purchase #4	$59.69	10.215%	$65.7873	$65.79	$65.80	$65.80
Purchase #5	$62.67	4.525%	$65.5058	$65.51	$65.50	$65.50
Purchase #6	$12.69	10.872%	$14.0697	$14.07	$14.05	$14.10
Purchase #7	$222.69	6.612%	$237.4143	$237.41	$237.40	$237.40
7 purchase totals =	$925.79		$1,008.2356	$1,008.24	$1,008.25	$1,008.20