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	$152.88	3.233%	$157.8226	$157.82	$157.80	$157.80
Purchase #2	$146.51	4.386%	$152.9359	$152.94	$152.95	$152.90
Purchase #3	$139.29	13.637%	$158.285	$158.29	$158.30	$158.30
Purchase #4	$48.29	4.435%	$50.4317	$50.43	$50.45	$50.40
Purchase #5	$165.58	12.293%	$185.9347	$185.93	$185.95	$185.90
Purchase #6	$40.34	5.871%	$42.7084	$42.71	$42.70	$42.70
Purchase #7	$123.49	7.548%	$132.811	$132.81	$132.80	$132.80
7 purchase totals =	$816.38		$880.9293	$880.93	$880.95	$880.80