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	$57.59	3.695%	$59.718	$59.72	$59.70	$59.70
Purchase #2	$204.39	11.115%	$227.1079	$227.11	$227.10	$227.10
Purchase #3	$32.91	10.338%	$36.3122	$36.31	$36.30	$36.30
Purchase #4	$150.74	13.851%	$171.619	$171.62	$171.60	$171.60
Purchase #5	$82.36	6.151%	$87.426	$87.43	$87.45	$87.40
Purchase #6	$227.33	12.725%	$256.2577	$256.26	$256.25	$256.30
Purchase #7	$40.77	4.396%	$42.5622	$42.56	$42.55	$42.60
7 purchase totals =	$796.09		$881.0030	$881.01	$880.95	$881.00