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	$146.42	4.294%	$152.7073	$152.71	$152.70	$152.70
Purchase #2	$7.78	8.545%	$8.4448	$8.44	$8.45	$8.40
Purchase #3	$139.95	12.830%	$157.9056	$157.91	$157.90	$157.90
Purchase #4	$55.38	8.149%	$59.8929	$59.89	$59.90	$59.90
Purchase #5	$100.93	4.513%	$105.485	$105.49	$105.50	$105.50
Purchase #6	$160.27	12.234%	$179.8774	$179.88	$179.90	$179.90
Purchase #7	$9.44	3.709%	$9.7901	$9.79	$9.80	$9.80
7 purchase totals =	$620.17		$674.1031	$674.11	$674.15	$674.10