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	$162.73	7.848%	$175.5011	$175.50	$175.50	$175.50
Purchase #2	$175.37	11.178%	$194.9729	$194.97	$194.95	$195.00
Purchase #3	$64.31	13.249%	$72.8304	$72.83	$72.85	$72.80
Purchase #4	$77.37	7.197%	$82.9383	$82.94	$82.95	$82.90
Purchase #5	$154.57	5.389%	$162.8998	$162.90	$162.90	$162.90
Purchase #6	$183.88	13.552%	$208.7994	$208.80	$208.80	$208.80
Purchase #7	$15.44	13.496%	$17.5238	$17.52	$17.50	$17.50
7 purchase totals =	$833.67		$915.4657	$915.46	$915.45	$915.40