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	$36.93	10.689%	$40.8774	$40.88	$40.90	$40.90
Purchase #2	$9.90	12.648%	$11.1522	$11.15	$11.15	$11.20
Purchase #3	$94.62	10.316%	$104.381	$104.38	$104.40	$104.40
Purchase #4	$15.86	10.674%	$17.5529	$17.55	$17.55	$17.60
Purchase #5	$141.37	11.728%	$157.9499	$157.95	$157.95	$157.90
Purchase #6	$237.86	12.212%	$266.9075	$266.91	$266.90	$266.90
Purchase #7	$188.32	10.608%	$208.297	$208.30	$208.30	$208.30
7 purchase totals =	$724.86		$807.1179	$807.12	$807.15	$807.20