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	$210.53	5.484%	$222.0755	$222.08	$222.10	$222.10
Purchase #2	$153.58	3.145%	$158.4101	$158.41	$158.40	$158.40
Purchase #3	$65.82	10.579%	$72.7831	$72.78	$72.80	$72.80
Purchase #4	$124.61	13.176%	$141.0286	$141.03	$141.05	$141.00
Purchase #5	$112.92	10.810%	$125.1267	$125.13	$125.15	$125.10
Purchase #6	$196.53	7.306%	$210.8885	$210.89	$210.90	$210.90
Purchase #7	$240.42	3.192%	$248.0942	$248.09	$248.10	$248.10
7 purchase totals =	$1,104.41		$1,178.4067	$1,178.41	$1,178.50	$1,178.40