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	$231.43	5.597%	$244.3831	$244.38	$244.40	$244.40
Purchase #2	$115.73	6.841%	$123.6471	$123.65	$123.65	$123.60
Purchase #3	$113.96	10.782%	$126.2472	$126.25	$126.25	$126.20
Purchase #4	$175.38	8.841%	$190.8853	$190.89	$190.90	$190.90
Purchase #5	$105.60	9.132%	$115.2434	$115.24	$115.25	$115.20
Purchase #6	$158.43	7.212%	$169.856	$169.86	$169.85	$169.90
Purchase #7	$165.51	5.781%	$175.0781	$175.08	$175.10	$175.10
7 purchase totals =	$1,066.04		$1,145.3402	$1,145.35	$1,145.40	$1,145.30