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	$231.88	12.622%	$261.1479	$261.15	$261.15	$261.10
Purchase #2	$66.90	5.692%	$70.7079	$70.71	$70.70	$70.70
Purchase #3	$161.26	5.252%	$169.7294	$169.73	$169.75	$169.70
Purchase #4	$170.55	11.718%	$190.535	$190.54	$190.55	$190.50
Purchase #5	$59.57	6.130%	$63.2216	$63.22	$63.20	$63.20
Purchase #6	$113.46	12.676%	$127.8422	$127.84	$127.85	$127.80
Purchase #7	$197.27	4.147%	$205.4508	$205.45	$205.45	$205.50
7 purchase totals =	$1,000.89		$1,088.6348	$1,088.64	$1,088.65	$1,088.50