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	$9.92	9.617%	$10.874	$10.87	$10.85	$10.90
Purchase #2	$125.95	3.634%	$130.527	$130.53	$130.55	$130.50
Purchase #3	$79.43	7.102%	$85.0711	$85.07	$85.05	$85.10
Purchase #4	$78.74	4.755%	$82.4841	$82.48	$82.50	$82.50
Purchase #5	$235.75	7.625%	$253.7259	$253.73	$253.75	$253.70
Purchase #6	$223.83	12.208%	$251.1552	$251.16	$251.15	$251.20
Purchase #7	$153.87	8.842%	$167.4752	$167.48	$167.50	$167.50
7 purchase totals =	$907.49		$981.3125	$981.32	$981.35	$981.40