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	$218.73	13.273%	$247.762	$247.76	$247.75	$247.80
Purchase #2	$209.76	6.432%	$223.2518	$223.25	$223.25	$223.30
Purchase #3	$23.33	4.321%	$24.3381	$24.34	$24.35	$24.30
Purchase #4	$161.29	10.225%	$177.7819	$177.78	$177.80	$177.80
Purchase #5	$91.38	10.156%	$100.6606	$100.66	$100.65	$100.70
Purchase #6	$33.58	5.450%	$35.4101	$35.41	$35.40	$35.40
Purchase #7	$196.52	12.874%	$221.82	$221.82	$221.80	$221.80
7 purchase totals =	$934.59		$1,031.0245	$1,031.02	$1,031.00	$1,031.10