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	$38.63	6.331%	$41.0757	$41.08	$41.10	$41.10
Purchase #2	$126.53	12.162%	$141.9186	$141.92	$141.90	$141.90
Purchase #3	$184.58	7.700%	$198.7927	$198.79	$198.80	$198.80
Purchase #4	$83.85	11.211%	$93.2504	$93.25	$93.25	$93.30
Purchase #5	$53.79	11.118%	$59.7704	$59.77	$59.75	$59.80
Purchase #6	$161.80	6.649%	$172.5581	$172.56	$172.55	$172.60
Purchase #7	$16.99	3.165%	$17.5277	$17.53	$17.55	$17.50
7 purchase totals =	$666.17		$724.8936	$724.90	$724.90	$725.00