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	$195.35	12.349%	$219.4738	$219.47	$219.45	$219.50
Purchase #2	$150.36	9.374%	$164.4547	$164.45	$164.45	$164.50
Purchase #3	$33.28	12.614%	$37.4779	$37.48	$37.50	$37.50
Purchase #4	$10.62	6.143%	$11.2724	$11.27	$11.25	$11.30
Purchase #5	$141.51	4.787%	$148.2841	$148.28	$148.30	$148.30
Purchase #6	$52.36	13.236%	$59.2904	$59.29	$59.30	$59.30
Purchase #7	$97.37	4.569%	$101.8188	$101.82	$101.80	$101.80
7 purchase totals =	$680.85		$742.0721	$742.06	$742.05	$742.20