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	$63.76	10.741%	$70.6085	$70.61	$70.60	$70.60
Purchase #2	$133.33	4.561%	$139.4112	$139.41	$139.40	$139.40
Purchase #3	$240.35	13.498%	$272.7924	$272.79	$272.80	$272.80
Purchase #4	$227.60	12.605%	$256.289	$256.29	$256.30	$256.30
Purchase #5	$76.25	3.314%	$78.7769	$78.78	$78.80	$78.80
Purchase #6	$239.66	5.620%	$253.1289	$253.13	$253.15	$253.10
Purchase #7	$32.98	6.405%	$35.0924	$35.09	$35.10	$35.10
7 purchase totals =	$1,013.93		$1,106.0993	$1,106.10	$1,106.15	$1,106.10