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	$225.27	13.851%	$256.4721	$256.47	$256.45	$256.50
Purchase #2	$27.85	3.345%	$28.7816	$28.78	$28.80	$28.80
Purchase #3	$247.34	8.284%	$267.8296	$267.83	$267.85	$267.80
Purchase #4	$56.83	10.167%	$62.6079	$62.61	$62.60	$62.60
Purchase #5	$89.26	9.795%	$98.003	$98.00	$98.00	$98.00
Purchase #6	$163.78	4.139%	$170.5589	$170.56	$170.55	$170.60
Purchase #7	$89.44	12.767%	$100.8588	$100.86	$100.85	$100.90
7 purchase totals =	$899.77		$985.1119	$985.11	$985.10	$985.20