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	$163.77	5.334%	$172.5055	$172.51	$172.50	$172.50
Purchase #2	$51.78	5.442%	$54.5979	$54.60	$54.60	$54.60
Purchase #3	$136.80	8.790%	$148.8247	$148.82	$148.80	$148.80
Purchase #4	$241.44	11.185%	$268.4451	$268.45	$268.45	$268.40
Purchase #5	$189.80	7.395%	$203.8357	$203.84	$203.85	$203.80
Purchase #6	$132.58	10.389%	$146.3537	$146.35	$146.35	$146.40
Purchase #7	$8.29	8.816%	$9.0208	$9.02	$9.00	$9.00
7 purchase totals =	$924.46		$1,003.5834	$1,003.59	$1,003.55	$1,003.50