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	$146.44	7.492%	$157.4113	$157.41	$157.40	$157.40
Purchase #2	$164.87	4.767%	$172.7294	$172.73	$172.75	$172.70
Purchase #3	$184.90	4.761%	$193.7031	$193.70	$193.70	$193.70
Purchase #4	$75.59	3.797%	$78.4602	$78.46	$78.45	$78.50
Purchase #5	$219.87	11.403%	$244.9418	$244.94	$244.95	$244.90
Purchase #6	$154.95	8.508%	$168.1331	$168.13	$168.15	$168.10
Purchase #7	$87.40	3.384%	$90.3576	$90.36	$90.35	$90.40
7 purchase totals =	$1,034.02		$1,105.7365	$1,105.73	$1,105.75	$1,105.70