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	$224.28	10.531%	$247.8989	$247.90	$247.90	$247.90
Purchase #2	$106.91	11.797%	$119.5222	$119.52	$119.50	$119.50
Purchase #3	$210.88	3.518%	$218.2988	$218.30	$218.30	$218.30
Purchase #4	$81.42	10.664%	$90.1026	$90.10	$90.10	$90.10
Purchase #5	$144.30	4.381%	$150.6218	$150.62	$150.60	$150.60
Purchase #6	$232.61	7.130%	$249.1951	$249.20	$249.20	$249.20
Purchase #7	$23.26	6.805%	$24.8428	$24.84	$24.85	$24.80
7 purchase totals =	$1,023.66		$1,100.4822	$1,100.48	$1,100.45	$1,100.40