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	$169.36	13.447%	$192.1338	$192.13	$192.15	$192.10
Purchase #2	$151.38	11.123%	$168.218	$168.22	$168.20	$168.20
Purchase #3	$19.74	13.129%	$22.3317	$22.33	$22.35	$22.30
Purchase #4	$133.84	4.499%	$139.8615	$139.86	$139.85	$139.90
Purchase #5	$39.66	13.863%	$45.1581	$45.16	$45.15	$45.20
Purchase #6	$62.38	4.468%	$65.1671	$65.17	$65.15	$65.20
Purchase #7	$140.75	9.322%	$153.8707	$153.87	$153.85	$153.90
7 purchase totals =	$717.11		$786.7409	$786.74	$786.70	$786.80