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	$91.57	11.573%	$102.1674	$102.17	$102.15	$102.20
Purchase #2	$246.55	13.814%	$280.6084	$280.61	$280.60	$280.60
Purchase #3	$240.78	6.677%	$256.8569	$256.86	$256.85	$256.90
Purchase #4	$204.82	4.117%	$213.2524	$213.25	$213.25	$213.30
Purchase #5	$71.63	12.422%	$80.5279	$80.53	$80.55	$80.50
Purchase #6	$67.62	3.194%	$69.7798	$69.78	$69.80	$69.80
Purchase #7	$11.76	8.585%	$12.7696	$12.77	$12.75	$12.80
7 purchase totals =	$934.73		$1,015.9624	$1,015.97	$1,015.95	$1,016.10