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	$161.42	4.841%	$169.2343	$169.23	$169.25	$169.20
Purchase #2	$35.76	11.763%	$39.9664	$39.97	$39.95	$40.00
Purchase #3	$106.56	3.333%	$110.1116	$110.11	$110.10	$110.10
Purchase #4	$18.59	11.151%	$20.663	$20.66	$20.65	$20.70
Purchase #5	$89.73	11.281%	$99.8524	$99.85	$99.85	$99.90
Purchase #6	$90.98	13.146%	$102.9402	$102.94	$102.95	$102.90
Purchase #7	$18.78	12.754%	$21.1752	$21.18	$21.20	$21.20
7 purchase totals =	$521.82		$563.9431	$563.94	$563.95	$564.00