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	$186.89	11.575%	$208.5225	$208.52	$208.50	$208.50
Purchase #2	$63.33	13.829%	$72.0879	$72.09	$72.10	$72.10
Purchase #3	$52.44	7.443%	$56.3431	$56.34	$56.35	$56.30
Purchase #4	$163.58	4.139%	$170.3506	$170.35	$170.35	$170.40
Purchase #5	$54.61	13.224%	$61.8316	$61.83	$61.85	$61.80
Purchase #6	$221.48	13.510%	$251.4019	$251.40	$251.40	$251.40
Purchase #7	$168.73	3.717%	$175.0017	$175.00	$175.00	$175.00
7 purchase totals =	$911.06		$995.5393	$995.53	$995.55	$995.50