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	$74.49	11.236%	$82.8597	$82.86	$82.85	$82.90
Purchase #2	$104.50	12.317%	$117.3713	$117.37	$117.35	$117.40
Purchase #3	$157.66	10.647%	$174.4461	$174.45	$174.45	$174.40
Purchase #4	$173.40	7.185%	$185.8588	$185.86	$185.85	$185.90
Purchase #5	$160.52	11.539%	$179.0424	$179.04	$179.05	$179.00
Purchase #6	$127.97	9.848%	$140.5725	$140.57	$140.55	$140.60
Purchase #7	$146.94	13.327%	$166.5227	$166.52	$166.50	$166.50
7 purchase totals =	$945.48		$1,046.6735	$1,046.67	$1,046.60	$1,046.70