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	$176.50	12.808%	$199.1061	$199.11	$199.10	$199.10
Purchase #2	$31.65	9.201%	$34.5621	$34.56	$34.55	$34.60
Purchase #3	$221.53	10.109%	$243.9245	$243.92	$243.90	$243.90
Purchase #4	$59.98	7.563%	$64.5163	$64.52	$64.50	$64.50
Purchase #5	$163.55	7.523%	$175.8539	$175.85	$175.85	$175.90
Purchase #6	$92.69	8.837%	$100.881	$100.88	$100.90	$100.90
Purchase #7	$53.26	11.440%	$59.3529	$59.35	$59.35	$59.40
7 purchase totals =	$799.16		$878.1968	$878.19	$878.15	$878.30