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	$158.53	9.339%	$173.3351	$173.34	$173.35	$173.30
Purchase #2	$12.77	8.740%	$13.8861	$13.89	$13.90	$13.90
Purchase #3	$76.74	7.202%	$82.2668	$82.27	$82.25	$82.30
Purchase #4	$75.43	9.323%	$82.4623	$82.46	$82.45	$82.50
Purchase #5	$248.32	4.300%	$258.9978	$259.00	$259.00	$259.00
Purchase #6	$24.93	8.799%	$27.1236	$27.12	$27.10	$27.10
Purchase #7	$136.69	12.252%	$153.4373	$153.44	$153.45	$153.40
7 purchase totals =	$733.41		$791.5090	$791.52	$791.50	$791.50