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	$200.69	11.308%	$223.384	$223.38	$223.40	$223.40
Purchase #2	$84.93	6.469%	$90.4241	$90.42	$90.40	$90.40
Purchase #3	$140.96	11.617%	$157.3353	$157.34	$157.35	$157.30
Purchase #4	$172.85	4.852%	$181.2367	$181.24	$181.25	$181.20
Purchase #5	$228.53	13.545%	$259.4844	$259.48	$259.50	$259.50
Purchase #6	$221.38	5.182%	$232.8519	$232.85	$232.85	$232.90
Purchase #7	$96.73	4.116%	$100.7114	$100.71	$100.70	$100.70
7 purchase totals =	$1,146.07		$1,245.4278	$1,245.42	$1,245.45	$1,245.40