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	$172.63	13.748%	$196.3632	$196.36	$196.35	$196.40
Purchase #2	$43.53	8.692%	$47.3136	$47.31	$47.30	$47.30
Purchase #3	$245.56	7.657%	$264.3625	$264.36	$264.35	$264.40
Purchase #4	$13.52	3.186%	$13.9507	$13.95	$13.95	$14.00
Purchase #5	$160.71	7.574%	$172.8822	$172.88	$172.90	$172.90
Purchase #6	$87.29	9.698%	$95.7554	$95.76	$95.75	$95.80
Purchase #7	$50.45	3.502%	$52.2168	$52.22	$52.20	$52.20
7 purchase totals =	$773.69		$842.8444	$842.84	$842.80	$843.00