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	$211.44	11.309%	$235.3517	$235.35	$235.35	$235.40
Purchase #2	$150.96	4.303%	$157.4558	$157.46	$157.45	$157.50
Purchase #3	$38.86	9.118%	$42.4033	$42.40	$42.40	$42.40
Purchase #4	$204.77	13.222%	$231.8447	$231.84	$231.85	$231.80
Purchase #5	$182.60	9.262%	$199.5124	$199.51	$199.50	$199.50
Purchase #6	$64.82	3.330%	$66.9785	$66.98	$67.00	$67.00
Purchase #7	$237.70	11.453%	$264.9238	$264.92	$264.90	$264.90
7 purchase totals =	$1,091.15		$1,198.4702	$1,198.46	$1,198.45	$1,198.50