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	$166.65	3.381%	$172.2844	$172.28	$172.30	$172.30
Purchase #2	$246.29	3.771%	$255.5776	$255.58	$255.60	$255.60
Purchase #3	$29.44	12.568%	$33.14	$33.14	$33.15	$33.10
Purchase #4	$201.50	6.547%	$214.6922	$214.69	$214.70	$214.70
Purchase #5	$109.78	5.540%	$115.8618	$115.86	$115.85	$115.90
Purchase #6	$62.56	7.503%	$67.2539	$67.25	$67.25	$67.30
Purchase #7	$146.98	13.187%	$166.3623	$166.36	$166.35	$166.40
7 purchase totals =	$963.20		$1,025.1722	$1,025.16	$1,025.20	$1,025.30