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	$35.55	4.512%	$37.154	$37.15	$37.15	$37.20
Purchase #2	$170.83	12.724%	$192.5664	$192.57	$192.55	$192.60
Purchase #3	$131.69	13.292%	$149.1942	$149.19	$149.20	$149.20
Purchase #4	$138.25	9.733%	$151.7059	$151.71	$151.70	$151.70
Purchase #5	$71.33	10.666%	$78.9381	$78.94	$78.95	$78.90
Purchase #6	$134.35	11.657%	$150.0112	$150.01	$150.00	$150.00
Purchase #7	$156.49	7.299%	$167.9122	$167.91	$167.90	$167.90
7 purchase totals =	$838.49		$927.4820	$927.48	$927.45	$927.50