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	$104.48	4.815%	$109.5107	$109.51	$109.50	$109.50
Purchase #2	$95.50	10.114%	$105.1589	$105.16	$105.15	$105.20
Purchase #3	$38.86	8.243%	$42.0632	$42.06	$42.05	$42.10
Purchase #4	$163.43	9.684%	$179.2566	$179.26	$179.25	$179.30
Purchase #5	$238.39	8.383%	$258.3742	$258.37	$258.35	$258.40
Purchase #6	$209.51	11.144%	$232.8578	$232.86	$232.85	$232.90
Purchase #7	$187.72	12.227%	$210.6725	$210.67	$210.65	$210.70
7 purchase totals =	$1,037.89		$1,137.8939	$1,137.89	$1,137.80	$1,138.10