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	$56.57	3.250%	$58.4085	$58.41	$58.40	$58.40
Purchase #2	$211.36	8.575%	$229.4841	$229.48	$229.50	$229.50
Purchase #3	$84.27	3.773%	$87.4495	$87.45	$87.45	$87.40
Purchase #4	$86.68	3.603%	$89.8031	$89.80	$89.80	$89.80
Purchase #5	$114.81	11.350%	$127.8409	$127.84	$127.85	$127.80
Purchase #6	$84.54	6.594%	$90.1146	$90.11	$90.10	$90.10
Purchase #7	$60.35	4.169%	$62.866	$62.87	$62.85	$62.90
7 purchase totals =	$698.58		$745.9667	$745.96	$745.95	$745.90