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	$86.55	9.856%	$95.0804	$95.08	$95.10	$95.10
Purchase #2	$100.68	5.443%	$106.16	$106.16	$106.15	$106.20
Purchase #3	$37.45	5.390%	$39.4686	$39.47	$39.45	$39.50
Purchase #4	$147.63	7.658%	$158.9355	$158.94	$158.95	$158.90
Purchase #5	$203.77	9.865%	$223.8719	$223.87	$223.85	$223.90
Purchase #6	$6.91	5.317%	$7.2774	$7.28	$7.30	$7.30
Purchase #7	$244.97	3.872%	$254.4552	$254.46	$254.45	$254.50
7 purchase totals =	$827.96		$885.2490	$885.26	$885.25	$885.40