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	$162.34	10.830%	$179.9214	$179.92	$179.90	$179.90
Purchase #2	$138.47	8.456%	$150.179	$150.18	$150.20	$150.20
Purchase #3	$27.99	13.767%	$31.8434	$31.84	$31.85	$31.80
Purchase #4	$143.97	12.379%	$161.792	$161.79	$161.80	$161.80
Purchase #5	$213.27	4.329%	$222.5025	$222.50	$222.50	$222.50
Purchase #6	$107.73	10.549%	$119.0944	$119.09	$119.10	$119.10
Purchase #7	$213.85	3.240%	$220.7787	$220.78	$220.80	$220.80
7 purchase totals =	$1,007.62		$1,086.1114	$1,086.10	$1,086.15	$1,086.10