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	$250.89	13.739%	$285.3598	$285.36	$285.35	$285.40
Purchase #2	$42.46	5.684%	$44.8734	$44.87	$44.85	$44.90
Purchase #3	$140.29	12.840%	$158.3032	$158.30	$158.30	$158.30
Purchase #4	$184.53	7.334%	$198.0634	$198.06	$198.05	$198.10
Purchase #5	$167.90	13.669%	$190.8503	$190.85	$190.85	$190.90
Purchase #6	$56.74	13.833%	$64.5888	$64.59	$64.60	$64.60
Purchase #7	$173.86	3.298%	$179.5939	$179.59	$179.60	$179.60
7 purchase totals =	$1,016.67		$1,121.6328	$1,121.62	$1,121.60	$1,121.80