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	$217.82	6.689%	$232.39	$232.39	$232.40	$232.40
Purchase #2	$80.39	8.552%	$87.265	$87.27	$87.25	$87.30
Purchase #3	$160.90	7.226%	$172.5266	$172.53	$172.55	$172.50
Purchase #4	$146.57	13.506%	$166.3657	$166.37	$166.35	$166.40
Purchase #5	$87.47	5.475%	$92.259	$92.26	$92.25	$92.30
Purchase #6	$177.76	6.360%	$189.0655	$189.07	$189.05	$189.10
Purchase #7	$93.49	6.455%	$99.5248	$99.52	$99.50	$99.50
7 purchase totals =	$964.40		$1,039.3966	$1,039.41	$1,039.35	$1,039.50