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	$160.32	7.306%	$172.033	$172.03	$172.05	$172.00
Purchase #2	$164.85	7.708%	$177.5566	$177.56	$177.55	$177.60
Purchase #3	$185.46	13.518%	$210.5305	$210.53	$210.55	$210.50
Purchase #4	$47.39	10.556%	$52.3925	$52.39	$52.40	$52.40
Purchase #5	$43.78	13.807%	$49.8247	$49.82	$49.80	$49.80
Purchase #6	$194.82	8.404%	$211.1927	$211.19	$211.20	$211.20
Purchase #7	$79.88	3.334%	$82.5432	$82.54	$82.55	$82.50
7 purchase totals =	$876.50		$956.0732	$956.06	$956.10	$956.00