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	$214.47	6.537%	$228.4899	$228.49	$228.50	$228.50
Purchase #2	$17.53	7.568%	$18.8567	$18.86	$18.85	$18.90
Purchase #3	$57.48	12.241%	$64.5161	$64.52	$64.50	$64.50
Purchase #4	$32.31	6.697%	$34.4738	$34.47	$34.45	$34.50
Purchase #5	$246.81	13.640%	$280.4749	$280.47	$280.45	$280.50
Purchase #6	$209.81	10.777%	$232.4212	$232.42	$232.40	$232.40
Purchase #7	$78.35	13.561%	$88.975	$88.98	$89.00	$89.00
7 purchase totals =	$856.76		$948.2076	$948.21	$948.15	$948.30