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	$87.26	8.274%	$94.4799	$94.48	$94.50	$94.50
Purchase #2	$85.39	7.413%	$91.72	$91.72	$91.70	$91.70
Purchase #3	$125.78	3.666%	$130.3911	$130.39	$130.40	$130.40
Purchase #4	$174.72	11.832%	$195.3929	$195.39	$195.40	$195.40
Purchase #5	$136.85	6.732%	$146.0627	$146.06	$146.05	$146.10
Purchase #6	$134.39	13.308%	$152.2746	$152.27	$152.25	$152.30
Purchase #7	$43.38	4.830%	$45.4753	$45.48	$45.50	$45.50
7 purchase totals =	$787.77		$855.7965	$855.79	$855.80	$855.90