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	$22.39	11.359%	$24.9333	$24.93	$24.95	$24.90
Purchase #2	$34.67	4.263%	$36.148	$36.15	$36.15	$36.10
Purchase #3	$93.49	4.306%	$97.5157	$97.52	$97.50	$97.50
Purchase #4	$140.40	13.173%	$158.8949	$158.89	$158.90	$158.90
Purchase #5	$99.25	12.669%	$111.824	$111.82	$111.80	$111.80
Purchase #6	$190.64	4.168%	$198.5859	$198.59	$198.60	$198.60
Purchase #7	$49.67	7.231%	$53.2616	$53.26	$53.25	$53.30
7 purchase totals =	$630.51		$681.1634	$681.16	$681.15	$681.10