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	$160.95	6.420%	$171.283	$171.28	$171.30	$171.30
Purchase #2	$70.30	8.804%	$76.4892	$76.49	$76.50	$76.50
Purchase #3	$37.33	3.186%	$38.5193	$38.52	$38.50	$38.50
Purchase #4	$137.53	9.596%	$150.7274	$150.73	$150.75	$150.70
Purchase #5	$64.88	11.541%	$72.3678	$72.37	$72.35	$72.40
Purchase #6	$250.66	13.766%	$285.1659	$285.17	$285.15	$285.20
Purchase #7	$107.34	3.651%	$111.259	$111.26	$111.25	$111.30
7 purchase totals =	$828.99		$905.8116	$905.82	$905.80	$905.90