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	$230.84	7.118%	$247.2712	$247.27	$247.25	$247.30
Purchase #2	$56.90	6.518%	$60.6087	$60.61	$60.60	$60.60
Purchase #3	$233.42	13.331%	$264.5372	$264.54	$264.55	$264.50
Purchase #4	$201.29	5.193%	$211.743	$211.74	$211.75	$211.70
Purchase #5	$61.57	9.518%	$67.4302	$67.43	$67.45	$67.40
Purchase #6	$64.37	5.274%	$67.7649	$67.76	$67.75	$67.80
Purchase #7	$172.96	4.147%	$180.1327	$180.13	$180.15	$180.10
7 purchase totals =	$1,021.35		$1,099.4879	$1,099.48	$1,099.50	$1,099.40