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	$119.69	11.476%	$133.4256	$133.43	$133.45	$133.40
Purchase #2	$53.94	6.308%	$57.3425	$57.34	$57.35	$57.30
Purchase #3	$17.91	4.264%	$18.6737	$18.67	$18.65	$18.70
Purchase #4	$142.79	13.401%	$161.9253	$161.93	$161.95	$161.90
Purchase #5	$78.93	4.399%	$82.4021	$82.40	$82.40	$82.40
Purchase #6	$214.92	7.699%	$231.4667	$231.47	$231.45	$231.50
Purchase #7	$40.41	10.334%	$44.586	$44.59	$44.60	$44.60
7 purchase totals =	$668.59		$729.8219	$729.83	$729.85	$729.80