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	$178.41	10.190%	$196.59	$196.59	$196.60	$196.60
Purchase #2	$161.65	13.561%	$183.5714	$183.57	$183.55	$183.60
Purchase #3	$200.72	10.648%	$222.0927	$222.09	$222.10	$222.10
Purchase #4	$208.29	5.793%	$220.3562	$220.36	$220.35	$220.40
Purchase #5	$20.32	11.264%	$22.6088	$22.61	$22.60	$22.60
Purchase #6	$53.73	8.519%	$58.3073	$58.31	$58.30	$58.30
Purchase #7	$52.32	3.569%	$54.1873	$54.19	$54.20	$54.20
7 purchase totals =	$875.44		$957.7137	$957.72	$957.70	$957.80