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	$104.70	11.220%	$116.4473	$116.45	$116.45	$116.40
Purchase #2	$202.47	3.503%	$209.5625	$209.56	$209.55	$209.60
Purchase #3	$102.88	13.329%	$116.5929	$116.59	$116.60	$116.60
Purchase #4	$151.67	11.583%	$169.2379	$169.24	$169.25	$169.20
Purchase #5	$29.79	12.349%	$33.4688	$33.47	$33.45	$33.50
Purchase #6	$77.52	6.751%	$82.7534	$82.75	$82.75	$82.80
Purchase #7	$184.80	8.601%	$200.6946	$200.69	$200.70	$200.70
7 purchase totals =	$853.83		$928.7574	$928.75	$928.75	$928.80