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	$125.59	12.706%	$141.5475	$141.55	$141.55	$141.50
Purchase #2	$119.31	7.687%	$128.4814	$128.48	$128.50	$128.50
Purchase #3	$49.53	10.217%	$54.5905	$54.59	$54.60	$54.60
Purchase #4	$212.87	10.485%	$235.1894	$235.19	$235.20	$235.20
Purchase #5	$169.71	13.311%	$192.3001	$192.30	$192.30	$192.30
Purchase #6	$123.39	13.119%	$139.5775	$139.58	$139.60	$139.60
Purchase #7	$148.38	10.594%	$164.0994	$164.10	$164.10	$164.10
7 purchase totals =	$948.78		$1,055.7858	$1,055.79	$1,055.85	$1,055.80