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	$39.62	9.185%	$43.2591	$43.26	$43.25	$43.30
Purchase #2	$44.79	6.666%	$47.7757	$47.78	$47.80	$47.80
Purchase #3	$6.40	8.310%	$6.9318	$6.93	$6.95	$6.90
Purchase #4	$76.96	10.495%	$85.037	$85.04	$85.05	$85.00
Purchase #5	$113.75	11.757%	$127.1236	$127.12	$127.10	$127.10
Purchase #6	$30.95	6.723%	$33.0308	$33.03	$33.05	$33.00
Purchase #7	$123.42	10.748%	$136.6852	$136.69	$136.70	$136.70
7 purchase totals =	$435.89		$479.8432	$479.85	$479.90	$479.80