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	$119.76	5.357%	$126.1755	$126.18	$126.20	$126.20
Purchase #2	$199.86	8.482%	$216.8121	$216.81	$216.80	$216.80
Purchase #3	$190.52	11.518%	$212.4641	$212.46	$212.45	$212.50
Purchase #4	$103.51	13.381%	$117.3607	$117.36	$117.35	$117.40
Purchase #5	$75.45	6.836%	$80.6078	$80.61	$80.60	$80.60
Purchase #6	$27.51	13.610%	$31.2541	$31.25	$31.25	$31.30
Purchase #7	$78.82	13.154%	$89.188	$89.19	$89.20	$89.20
7 purchase totals =	$795.43		$873.8623	$873.86	$873.85	$874.00