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	$139.28	10.261%	$153.5715	$153.57	$153.55	$153.60
Purchase #2	$34.91	8.650%	$37.9297	$37.93	$37.95	$37.90
Purchase #3	$160.80	6.497%	$171.2472	$171.25	$171.25	$171.20
Purchase #4	$6.82	6.812%	$7.2846	$7.28	$7.30	$7.30
Purchase #5	$143.59	4.673%	$150.3	$150.30	$150.30	$150.30
Purchase #6	$194.42	12.772%	$219.2513	$219.25	$219.25	$219.30
Purchase #7	$45.56	3.522%	$47.1646	$47.16	$47.15	$47.20
7 purchase totals =	$725.38		$786.7489	$786.74	$786.75	$786.80