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	$69.67	9.442%	$76.2482	$76.25	$76.25	$76.20
Purchase #2	$143.46	5.496%	$151.3446	$151.34	$151.35	$151.30
Purchase #3	$133.87	12.720%	$150.8983	$150.90	$150.90	$150.90
Purchase #4	$38.70	6.827%	$41.342	$41.34	$41.35	$41.30
Purchase #5	$152.72	10.380%	$168.5723	$168.57	$168.55	$168.60
Purchase #6	$10.39	7.537%	$11.1731	$11.17	$11.15	$11.20
Purchase #7	$208.80	7.465%	$224.3869	$224.39	$224.40	$224.40
7 purchase totals =	$757.61		$823.9654	$823.96	$823.95	$823.90