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	$60.30	12.796%	$68.016	$68.02	$68.00	$68.00
Purchase #2	$80.98	3.555%	$83.8588	$83.86	$83.85	$83.90
Purchase #3	$121.82	11.543%	$135.8817	$135.88	$135.90	$135.90
Purchase #4	$99.75	11.732%	$111.4527	$111.45	$111.45	$111.50
Purchase #5	$214.61	10.590%	$237.3372	$237.34	$237.35	$237.30
Purchase #6	$38.61	10.805%	$42.7818	$42.78	$42.80	$42.80
Purchase #7	$170.64	12.401%	$191.8011	$191.80	$191.80	$191.80
7 purchase totals =	$786.71		$871.1293	$871.13	$871.15	$871.20