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	$164.93	11.284%	$183.5407	$183.54	$183.55	$183.50
Purchase #2	$113.92	8.383%	$123.4699	$123.47	$123.45	$123.50
Purchase #3	$26.61	3.636%	$27.5775	$27.58	$27.60	$27.60
Purchase #4	$219.78	10.651%	$243.1888	$243.19	$243.20	$243.20
Purchase #5	$124.67	12.159%	$139.8286	$139.83	$139.85	$139.80
Purchase #6	$244.67	10.741%	$270.95	$270.95	$270.95	$271.00
Purchase #7	$178.76	6.455%	$190.299	$190.30	$190.30	$190.30
7 purchase totals =	$1,073.34		$1,178.8545	$1,178.86	$1,178.90	$1,178.90