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	$84.64	4.405%	$88.3684	$88.37	$88.35	$88.40
Purchase #2	$76.71	6.702%	$81.8511	$81.85	$81.85	$81.90
Purchase #3	$62.25	6.794%	$66.4793	$66.48	$66.50	$66.50
Purchase #4	$215.68	7.704%	$232.296	$232.30	$232.30	$232.30
Purchase #5	$83.45	7.780%	$89.9424	$89.94	$89.95	$89.90
Purchase #6	$25.43	9.123%	$27.75	$27.75	$27.75	$27.80
Purchase #7	$172.74	7.369%	$185.4692	$185.47	$185.45	$185.50
7 purchase totals =	$720.90		$772.1564	$772.16	$772.15	$772.30