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	$170.90	8.526%	$185.4709	$185.47	$185.45	$185.50
Purchase #2	$145.29	9.211%	$158.6727	$158.67	$158.65	$158.70
Purchase #3	$131.78	3.300%	$136.1287	$136.13	$136.15	$136.10
Purchase #4	$152.51	10.388%	$168.3527	$168.35	$168.35	$168.40
Purchase #5	$60.84	6.657%	$64.8901	$64.89	$64.90	$64.90
Purchase #6	$110.50	9.381%	$120.866	$120.87	$120.85	$120.90
Purchase #7	$180.65	13.185%	$204.4687	$204.47	$204.45	$204.50
7 purchase totals =	$952.47		$1,038.8498	$1,038.85	$1,038.80	$1,039.00