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	$147.26	7.575%	$158.4149	$158.41	$158.40	$158.40
Purchase #2	$131.63	11.551%	$146.8346	$146.83	$146.85	$146.80
Purchase #3	$227.91	12.505%	$256.4101	$256.41	$256.40	$256.40
Purchase #4	$59.92	9.634%	$65.6927	$65.69	$65.70	$65.70
Purchase #5	$98.50	9.550%	$107.9068	$107.91	$107.90	$107.90
Purchase #6	$208.27	4.742%	$218.1462	$218.15	$218.15	$218.10
Purchase #7	$233.46	9.534%	$255.7181	$255.72	$255.70	$255.70
7 purchase totals =	$1,106.95		$1,209.1234	$1,209.12	$1,209.10	$1,209.00