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	$240.93	8.386%	$261.1344	$261.13	$261.15	$261.10
Purchase #2	$20.28	5.332%	$21.3613	$21.36	$21.35	$21.40
Purchase #3	$145.37	5.496%	$153.3595	$153.36	$153.35	$153.40
Purchase #4	$246.25	11.437%	$274.4136	$274.41	$274.40	$274.40
Purchase #5	$100.70	10.335%	$111.1073	$111.11	$111.10	$111.10
Purchase #6	$85.69	5.191%	$90.1382	$90.14	$90.15	$90.10
Purchase #7	$95.51	10.864%	$105.8862	$105.89	$105.90	$105.90
7 purchase totals =	$934.73		$1,017.4005	$1,017.40	$1,017.40	$1,017.40