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	$56.57	11.838%	$63.2668	$63.27	$63.25	$63.30
Purchase #2	$33.95	11.428%	$37.8298	$37.83	$37.85	$37.80
Purchase #3	$79.60	3.572%	$82.4433	$82.44	$82.45	$82.40
Purchase #4	$87.98	5.592%	$92.8998	$92.90	$92.90	$92.90
Purchase #5	$186.44	6.738%	$199.0023	$199.00	$199.00	$199.00
Purchase #6	$139.69	6.546%	$148.8341	$148.83	$148.85	$148.80
Purchase #7	$85.90	6.134%	$91.1691	$91.17	$91.15	$91.20
7 purchase totals =	$670.13		$715.4452	$715.44	$715.45	$715.40