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	$43.49	4.469%	$45.4336	$45.43	$45.45	$45.40
Purchase #2	$32.75	11.466%	$36.5051	$36.51	$36.50	$36.50
Purchase #3	$37.56	4.276%	$39.1661	$39.17	$39.15	$39.20
Purchase #4	$222.88	9.850%	$244.8337	$244.83	$244.85	$244.80
Purchase #5	$31.83	6.394%	$33.8652	$33.87	$33.85	$33.90
Purchase #6	$27.56	3.782%	$28.6023	$28.60	$28.60	$28.60
Purchase #7	$87.90	3.571%	$91.0389	$91.04	$91.05	$91.00
7 purchase totals =	$483.97		$519.4449	$519.45	$519.45	$519.40