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	$102.70	9.772%	$112.7358	$112.74	$112.75	$112.70
Purchase #2	$187.89	6.390%	$199.8962	$199.90	$199.90	$199.90
Purchase #3	$190.74	10.433%	$210.6399	$210.64	$210.65	$210.60
Purchase #4	$98.85	6.570%	$105.3444	$105.34	$105.35	$105.30
Purchase #5	$100.36	5.171%	$105.5496	$105.55	$105.55	$105.50
Purchase #6	$160.34	7.553%	$172.4505	$172.45	$172.45	$172.50
Purchase #7	$196.32	11.284%	$218.4727	$218.47	$218.45	$218.50
7 purchase totals =	$1,037.20		$1,125.0891	$1,125.09	$1,125.10	$1,125.00