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	$117.75	8.460%	$127.7117	$127.71	$127.70	$127.70
Purchase #2	$59.86	10.706%	$66.2686	$66.27	$66.25	$66.30
Purchase #3	$32.65	3.296%	$33.7261	$33.73	$33.75	$33.70
Purchase #4	$225.75	4.605%	$236.1458	$236.15	$236.15	$236.10
Purchase #5	$170.30	10.297%	$187.8358	$187.84	$187.85	$187.80
Purchase #6	$248.39	13.670%	$282.3449	$282.34	$282.35	$282.30
Purchase #7	$61.37	9.726%	$67.3388	$67.34	$67.35	$67.30
7 purchase totals =	$916.07		$1,001.3717	$1,001.38	$1,001.40	$1,001.20