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	$72.65	13.335%	$82.3379	$82.34	$82.35	$82.30
Purchase #2	$214.57	13.775%	$244.127	$244.13	$244.15	$244.10
Purchase #3	$208.45	6.238%	$221.4531	$221.45	$221.45	$221.50
Purchase #4	$172.93	13.288%	$195.9089	$195.91	$195.90	$195.90
Purchase #5	$16.66	13.622%	$18.9294	$18.93	$18.95	$18.90
Purchase #6	$51.71	5.554%	$54.582	$54.58	$54.60	$54.60
Purchase #7	$88.69	12.616%	$99.8791	$99.88	$99.90	$99.90
7 purchase totals =	$825.66		$917.2174	$917.22	$917.30	$917.20