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	$146.31	10.537%	$161.7267	$161.73	$161.75	$161.70
Purchase #2	$234.76	11.472%	$261.6917	$261.69	$261.70	$261.70
Purchase #3	$102.74	8.833%	$111.815	$111.82	$111.80	$111.80
Purchase #4	$24.78	4.468%	$25.8872	$25.89	$25.90	$25.90
Purchase #5	$94.35	12.655%	$106.29	$106.29	$106.30	$106.30
Purchase #6	$50.51	6.436%	$53.7608	$53.76	$53.75	$53.80
Purchase #7	$127.78	8.803%	$139.0285	$139.03	$139.05	$139.00
7 purchase totals =	$781.23		$860.1999	$860.21	$860.25	$860.20