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	$40.48	3.347%	$41.8349	$41.83	$41.85	$41.80
Purchase #2	$64.77	13.502%	$73.5152	$73.52	$73.50	$73.50
Purchase #3	$18.42	3.632%	$19.089	$19.09	$19.10	$19.10
Purchase #4	$35.89	3.445%	$37.1264	$37.13	$37.15	$37.10
Purchase #5	$87.58	6.775%	$93.5135	$93.51	$93.50	$93.50
Purchase #6	$238.46	11.277%	$265.3511	$265.35	$265.35	$265.40
Purchase #7	$63.32	4.334%	$66.0643	$66.06	$66.05	$66.10
7 purchase totals =	$548.92		$596.4944	$596.49	$596.50	$596.50