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	$209.66	11.131%	$232.9973	$233.00	$233.00	$233.00
Purchase #2	$94.43	12.103%	$105.8589	$105.86	$105.85	$105.90
Purchase #3	$146.54	5.835%	$155.0906	$155.09	$155.10	$155.10
Purchase #4	$55.64	3.347%	$57.5023	$57.50	$57.50	$57.50
Purchase #5	$240.81	8.575%	$261.4595	$261.46	$261.45	$261.50
Purchase #6	$205.87	13.440%	$233.5389	$233.54	$233.55	$233.50
Purchase #7	$134.37	8.870%	$146.2886	$146.29	$146.30	$146.30
7 purchase totals =	$1,087.32		$1,192.7361	$1,192.74	$1,192.75	$1,192.80