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	$102.29	4.160%	$106.5453	$106.55	$106.55	$106.50
Purchase #2	$185.31	5.337%	$195.2	$195.20	$195.20	$195.20
Purchase #3	$91.86	10.483%	$101.4897	$101.49	$101.50	$101.50
Purchase #4	$132.40	3.822%	$137.4603	$137.46	$137.45	$137.50
Purchase #5	$232.69	13.600%	$264.3358	$264.34	$264.35	$264.30
Purchase #6	$152.59	13.851%	$173.7252	$173.73	$173.75	$173.70
Purchase #7	$144.57	5.410%	$152.3912	$152.39	$152.40	$152.40
7 purchase totals =	$1,041.71		$1,131.1475	$1,131.16	$1,131.20	$1,131.10