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	$50.64	3.451%	$52.3876	$52.39	$52.40	$52.40
Purchase #2	$180.92	4.649%	$189.331	$189.33	$189.35	$189.30
Purchase #3	$103.48	11.330%	$115.2043	$115.20	$115.20	$115.20
Purchase #4	$139.39	3.605%	$144.415	$144.42	$144.40	$144.40
Purchase #5	$196.61	13.198%	$222.5586	$222.56	$222.55	$222.60
Purchase #6	$17.27	7.144%	$18.5038	$18.50	$18.50	$18.50
Purchase #7	$206.95	8.674%	$224.9008	$224.90	$224.90	$224.90
7 purchase totals =	$895.26		$967.3011	$967.30	$967.30	$967.30