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	$151.32	13.171%	$171.2504	$171.25	$171.25	$171.30
Purchase #2	$13.89	6.643%	$14.8127	$14.81	$14.80	$14.80
Purchase #3	$20.51	6.404%	$21.8235	$21.82	$21.80	$21.80
Purchase #4	$58.38	10.172%	$64.3184	$64.32	$64.30	$64.30
Purchase #5	$216.98	8.749%	$235.9636	$235.96	$235.95	$236.00
Purchase #6	$244.71	5.810%	$258.9277	$258.93	$258.95	$258.90
Purchase #7	$23.90	5.294%	$25.1653	$25.17	$25.15	$25.20
7 purchase totals =	$729.69		$792.2616	$792.26	$792.20	$792.30