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	$133.50	13.162%	$151.0713	$151.07	$151.05	$151.10
Purchase #2	$73.48	6.342%	$78.1401	$78.14	$78.15	$78.10
Purchase #3	$72.76	9.619%	$79.7588	$79.76	$79.75	$79.80
Purchase #4	$58.43	6.420%	$62.1812	$62.18	$62.20	$62.20
Purchase #5	$149.54	3.764%	$155.1687	$155.17	$155.15	$155.20
Purchase #6	$23.71	8.856%	$25.8098	$25.81	$25.80	$25.80
Purchase #7	$137.54	11.859%	$153.8509	$153.85	$153.85	$153.90
7 purchase totals =	$648.96		$705.9808	$705.98	$705.95	$706.10