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	$202.78	6.540%	$216.0418	$216.04	$216.05	$216.00
Purchase #2	$222.87	9.707%	$244.504	$244.50	$244.50	$244.50
Purchase #3	$214.28	5.165%	$225.3476	$225.35	$225.35	$225.30
Purchase #4	$69.71	12.700%	$78.5632	$78.56	$78.55	$78.60
Purchase #5	$208.69	4.152%	$217.3548	$217.35	$217.35	$217.40
Purchase #6	$159.64	5.123%	$167.8184	$167.82	$167.80	$167.80
Purchase #7	$29.97	6.841%	$32.0202	$32.02	$32.00	$32.00
7 purchase totals =	$1,107.94		$1,181.6500	$1,181.64	$1,181.60	$1,181.60