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	$125.29	11.104%	$139.2022	$139.20	$139.20	$139.20
Purchase #2	$39.94	13.698%	$45.411	$45.41	$45.40	$45.40
Purchase #3	$111.82	7.210%	$119.8822	$119.88	$119.90	$119.90
Purchase #4	$206.88	4.406%	$215.9951	$216.00	$216.00	$216.00
Purchase #5	$217.37	7.310%	$233.2597	$233.26	$233.25	$233.30
Purchase #6	$131.33	11.813%	$146.844	$146.84	$146.85	$146.80
Purchase #7	$232.89	5.841%	$246.4931	$246.49	$246.50	$246.50
7 purchase totals =	$1,065.52		$1,147.0873	$1,147.08	$1,147.10	$1,147.10