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	$108.60	3.238%	$112.1165	$112.12	$112.10	$112.10
Purchase #2	$151.49	4.689%	$158.5934	$158.59	$158.60	$158.60
Purchase #3	$104.87	8.873%	$114.1751	$114.18	$114.20	$114.20
Purchase #4	$232.68	9.112%	$253.8818	$253.88	$253.90	$253.90
Purchase #5	$190.43	12.285%	$213.8243	$213.82	$213.80	$213.80
Purchase #6	$208.43	8.194%	$225.5088	$225.51	$225.50	$225.50
Purchase #7	$29.72	9.359%	$32.5015	$32.50	$32.50	$32.50
7 purchase totals =	$1,026.22		$1,110.6014	$1,110.60	$1,110.60	$1,110.60