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	$247.39	8.293%	$267.9061	$267.91	$267.90	$267.90
Purchase #2	$86.76	10.199%	$95.6087	$95.61	$95.60	$95.60
Purchase #3	$41.75	8.847%	$45.4436	$45.44	$45.45	$45.40
Purchase #4	$59.35	13.408%	$67.3076	$67.31	$67.30	$67.30
Purchase #5	$136.82	11.683%	$152.8047	$152.80	$152.80	$152.80
Purchase #6	$56.88	5.149%	$59.8088	$59.81	$59.80	$59.80
Purchase #7	$198.57	6.295%	$211.07	$211.07	$211.05	$211.10
7 purchase totals =	$827.52		$899.9495	$899.95	$899.90	$899.90