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	$94.85	4.740%	$99.3459	$99.35	$99.35	$99.30
Purchase #2	$49.50	9.558%	$54.2312	$54.23	$54.25	$54.20
Purchase #3	$130.40	12.556%	$146.773	$146.77	$146.75	$146.80
Purchase #4	$212.71	4.358%	$221.9799	$221.98	$222.00	$222.00
Purchase #5	$162.41	3.786%	$168.5588	$168.56	$168.55	$168.60
Purchase #6	$247.84	13.849%	$282.1634	$282.16	$282.15	$282.20
Purchase #7	$201.69	6.373%	$214.5437	$214.54	$214.55	$214.50
7 purchase totals =	$1,099.40		$1,187.5959	$1,187.59	$1,187.60	$1,187.60