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	$35.70	4.275%	$37.2262	$37.23	$37.25	$37.20
Purchase #2	$245.96	13.133%	$278.2619	$278.26	$278.25	$278.30
Purchase #3	$29.65	11.420%	$33.036	$33.04	$33.05	$33.00
Purchase #4	$60.81	9.716%	$66.7183	$66.72	$66.70	$66.70
Purchase #5	$35.91	9.800%	$39.4292	$39.43	$39.45	$39.40
Purchase #6	$109.56	6.706%	$116.9071	$116.91	$116.90	$116.90
Purchase #7	$86.85	9.781%	$95.3448	$95.34	$95.35	$95.30
7 purchase totals =	$604.44		$666.9235	$666.93	$666.95	$666.80