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	$77.66	10.110%	$85.5114	$85.51	$85.50	$85.50
Purchase #2	$152.47	9.543%	$167.0202	$167.02	$167.00	$167.00
Purchase #3	$152.82	3.108%	$157.5696	$157.57	$157.55	$157.60
Purchase #4	$40.27	4.302%	$42.0024	$42.00	$42.00	$42.00
Purchase #5	$90.71	13.525%	$102.9785	$102.98	$103.00	$103.00
Purchase #6	$75.65	13.417%	$85.8	$85.80	$85.80	$85.80
Purchase #7	$66.32	3.719%	$68.7864	$68.79	$68.80	$68.80
7 purchase totals =	$655.90		$709.6685	$709.67	$709.65	$709.70