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	$40.98	13.173%	$46.3783	$46.38	$46.40	$46.40
Purchase #2	$40.49	11.835%	$45.282	$45.28	$45.30	$45.30
Purchase #3	$78.83	3.864%	$81.876	$81.88	$81.90	$81.90
Purchase #4	$211.33	5.390%	$222.7207	$222.72	$222.70	$222.70
Purchase #5	$217.40	3.515%	$225.0416	$225.04	$225.05	$225.00
Purchase #6	$29.42	10.171%	$32.4123	$32.41	$32.40	$32.40
Purchase #7	$97.50	5.685%	$103.0429	$103.04	$103.05	$103.00
7 purchase totals =	$715.95		$756.7538	$756.75	$756.80	$756.70