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	$18.62	3.863%	$19.3393	$19.34	$19.35	$19.30
Purchase #2	$17.42	8.542%	$18.908	$18.91	$18.90	$18.90
Purchase #3	$40.75	11.417%	$45.4024	$45.40	$45.40	$45.40
Purchase #4	$176.67	11.258%	$196.5595	$196.56	$196.55	$196.60
Purchase #5	$33.69	13.228%	$38.1465	$38.15	$38.15	$38.10
Purchase #6	$139.69	9.221%	$152.5708	$152.57	$152.55	$152.60
Purchase #7	$180.65	11.536%	$201.4898	$201.49	$201.50	$201.50
7 purchase totals =	$607.49		$672.4163	$672.42	$672.40	$672.40