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	$213.83	5.664%	$225.9413	$225.94	$225.95	$225.90
Purchase #2	$139.73	7.668%	$150.4445	$150.44	$150.45	$150.40
Purchase #3	$157.32	10.363%	$173.6231	$173.62	$173.60	$173.60
Purchase #4	$172.54	9.274%	$188.5414	$188.54	$188.55	$188.50
Purchase #5	$12.42	6.446%	$13.2206	$13.22	$13.20	$13.20
Purchase #6	$8.69	8.331%	$9.414	$9.41	$9.40	$9.40
Purchase #7	$64.93	11.593%	$72.4573	$72.46	$72.45	$72.50
7 purchase totals =	$769.46		$833.6422	$833.63	$833.60	$833.50