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	$88.42	6.478%	$94.1478	$94.15	$94.15	$94.10
Purchase #2	$87.98	3.300%	$90.8833	$90.88	$90.90	$90.90
Purchase #3	$24.56	9.704%	$26.9433	$26.94	$26.95	$26.90
Purchase #4	$62.78	4.365%	$65.5203	$65.52	$65.50	$65.50
Purchase #5	$13.50	6.219%	$14.3396	$14.34	$14.35	$14.30
Purchase #6	$58.26	10.624%	$64.4495	$64.45	$64.45	$64.40
Purchase #7	$197.46	7.297%	$211.8687	$211.87	$211.85	$211.90
7 purchase totals =	$532.96		$568.1525	$568.15	$568.15	$568.00