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	$202.44	9.702%	$222.0807	$222.08	$222.10	$222.10
Purchase #2	$230.79	10.863%	$255.8607	$255.86	$255.85	$255.90
Purchase #3	$161.75	4.208%	$168.5564	$168.56	$168.55	$168.60
Purchase #4	$229.34	13.297%	$259.8353	$259.84	$259.85	$259.80
Purchase #5	$73.36	12.256%	$82.351	$82.35	$82.35	$82.40
Purchase #6	$123.62	5.285%	$130.1533	$130.15	$130.15	$130.20
Purchase #7	$84.53	13.522%	$95.9601	$95.96	$95.95	$96.00
7 purchase totals =	$1,105.83		$1,214.7975	$1,214.80	$1,214.80	$1,215.00