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	$66.47	8.682%	$72.2409	$72.24	$72.25	$72.20
Purchase #2	$237.25	7.518%	$255.0865	$255.09	$255.10	$255.10
Purchase #3	$100.75	13.802%	$114.6555	$114.66	$114.65	$114.70
Purchase #4	$6.52	13.384%	$7.3926	$7.39	$7.40	$7.40
Purchase #5	$35.35	8.857%	$38.4809	$38.48	$38.50	$38.50
Purchase #6	$96.75	13.757%	$110.0599	$110.06	$110.05	$110.10
Purchase #7	$122.64	6.741%	$130.9072	$130.91	$130.90	$130.90
7 purchase totals =	$665.73		$728.8235	$728.83	$728.85	$728.90