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	$118.55	9.640%	$129.9782	$129.98	$130.00	$130.00
Purchase #2	$64.72	11.418%	$72.1097	$72.11	$72.10	$72.10
Purchase #3	$83.89	11.392%	$93.4467	$93.45	$93.45	$93.40
Purchase #4	$172.66	5.741%	$182.5724	$182.57	$182.55	$182.60
Purchase #5	$37.79	4.365%	$39.4395	$39.44	$39.45	$39.40
Purchase #6	$39.28	9.861%	$43.1534	$43.15	$43.15	$43.20
Purchase #7	$129.53	11.553%	$144.4946	$144.49	$144.50	$144.50
7 purchase totals =	$646.42		$705.1945	$705.19	$705.20	$705.20