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	$8.69	7.390%	$9.3322	$9.33	$9.35	$9.30
Purchase #2	$41.78	13.714%	$47.5097	$47.51	$47.50	$47.50
Purchase #3	$6.71	10.618%	$7.4225	$7.42	$7.40	$7.40
Purchase #4	$168.30	10.569%	$186.0876	$186.09	$186.10	$186.10
Purchase #5	$100.83	10.626%	$111.5442	$111.54	$111.55	$111.50
Purchase #6	$215.76	8.230%	$233.517	$233.52	$233.50	$233.50
Purchase #7	$177.54	6.402%	$188.9061	$188.91	$188.90	$188.90
7 purchase totals =	$719.61		$784.3193	$784.32	$784.30	$784.20