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	$75.94	6.403%	$80.8024	$80.80	$80.80	$80.80
Purchase #2	$99.72	5.599%	$105.3033	$105.30	$105.30	$105.30
Purchase #3	$94.57	10.725%	$104.7126	$104.71	$104.70	$104.70
Purchase #4	$144.34	3.648%	$149.6055	$149.61	$149.60	$149.60
Purchase #5	$152.93	6.533%	$162.9209	$162.92	$162.90	$162.90
Purchase #6	$158.31	4.318%	$165.1458	$165.15	$165.15	$165.10
Purchase #7	$187.57	4.752%	$196.4833	$196.48	$196.50	$196.50
7 purchase totals =	$913.38		$964.9738	$964.97	$964.95	$964.90