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	$227.50	6.138%	$241.464	$241.46	$241.45	$241.50
Purchase #2	$124.96	5.447%	$131.7666	$131.77	$131.75	$131.80
Purchase #3	$104.38	6.723%	$111.3975	$111.40	$111.40	$111.40
Purchase #4	$135.88	7.510%	$146.0846	$146.08	$146.10	$146.10
Purchase #5	$176.33	12.841%	$198.9725	$198.97	$198.95	$199.00
Purchase #6	$98.39	10.796%	$109.0122	$109.01	$109.00	$109.00
Purchase #7	$141.89	4.845%	$148.7646	$148.76	$148.75	$148.80
7 purchase totals =	$1,009.33		$1,087.4620	$1,087.45	$1,087.40	$1,087.60