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	$218.59	12.355%	$245.5968	$245.60	$245.60	$245.60
Purchase #2	$28.71	9.638%	$31.4771	$31.48	$31.50	$31.50
Purchase #3	$89.86	13.813%	$102.2724	$102.27	$102.25	$102.30
Purchase #4	$143.45	3.654%	$148.6917	$148.69	$148.70	$148.70
Purchase #5	$48.47	7.210%	$51.9647	$51.96	$51.95	$52.00
Purchase #6	$115.75	6.702%	$123.5076	$123.51	$123.50	$123.50
Purchase #7	$141.45	7.163%	$151.5821	$151.58	$151.60	$151.60
7 purchase totals =	$786.28		$855.0924	$855.09	$855.10	$855.20