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	$110.92	7.516%	$119.2567	$119.26	$119.25	$119.30
Purchase #2	$177.45	10.869%	$196.737	$196.74	$196.75	$196.70
Purchase #3	$103.28	9.540%	$113.1329	$113.13	$113.15	$113.10
Purchase #4	$217.30	10.834%	$240.8423	$240.84	$240.85	$240.80
Purchase #5	$199.52	12.626%	$224.7114	$224.71	$224.70	$224.70
Purchase #6	$127.56	7.648%	$137.3158	$137.32	$137.30	$137.30
Purchase #7	$76.68	3.724%	$79.5356	$79.54	$79.55	$79.50
7 purchase totals =	$1,012.71		$1,111.5317	$1,111.54	$1,111.55	$1,111.40