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	$197.40	10.371%	$217.8724	$217.87	$217.85	$217.90
Purchase #2	$78.77	12.428%	$88.5595	$88.56	$88.55	$88.60
Purchase #3	$33.72	8.240%	$36.4985	$36.50	$36.50	$36.50
Purchase #4	$38.92	7.721%	$41.925	$41.93	$41.95	$41.90
Purchase #5	$65.84	9.744%	$72.2554	$72.26	$72.25	$72.30
Purchase #6	$227.29	10.389%	$250.9032	$250.90	$250.90	$250.90
Purchase #7	$34.30	3.590%	$35.5314	$35.53	$35.55	$35.50
7 purchase totals =	$676.24		$743.5454	$743.55	$743.55	$743.60