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	$132.97	5.565%	$140.3698	$140.37	$140.35	$140.40
Purchase #2	$72.64	5.866%	$76.9011	$76.90	$76.90	$76.90
Purchase #3	$231.97	7.818%	$250.1054	$250.11	$250.10	$250.10
Purchase #4	$114.49	13.162%	$129.5592	$129.56	$129.55	$129.60
Purchase #5	$174.37	12.496%	$196.1593	$196.16	$196.15	$196.20
Purchase #6	$234.78	5.733%	$248.2399	$248.24	$248.25	$248.20
Purchase #7	$18.26	10.732%	$20.2197	$20.22	$20.20	$20.20
7 purchase totals =	$979.48		$1,061.5544	$1,061.56	$1,061.50	$1,061.60