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	$132.56	6.789%	$141.5595	$141.56	$141.55	$141.60
Purchase #2	$23.99	12.342%	$26.9508	$26.95	$26.95	$27.00
Purchase #3	$185.61	6.820%	$198.2686	$198.27	$198.25	$198.30
Purchase #4	$79.85	11.649%	$89.1517	$89.15	$89.15	$89.20
Purchase #5	$29.29	10.518%	$32.3707	$32.37	$32.35	$32.40
Purchase #6	$19.82	9.333%	$21.6698	$21.67	$21.65	$21.70
Purchase #7	$187.73	11.474%	$209.2701	$209.27	$209.25	$209.30
7 purchase totals =	$658.85		$719.2412	$719.24	$719.15	$719.50