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	$132.62	6.215%	$140.8623	$140.86	$140.85	$140.90
Purchase #2	$13.32	6.430%	$14.1765	$14.18	$14.20	$14.20
Purchase #3	$147.75	6.614%	$157.5222	$157.52	$157.50	$157.50
Purchase #4	$70.51	11.365%	$78.5235	$78.52	$78.50	$78.50
Purchase #5	$73.42	11.660%	$81.9808	$81.98	$82.00	$82.00
Purchase #6	$12.93	4.349%	$13.4923	$13.49	$13.50	$13.50
Purchase #7	$217.95	7.622%	$234.5621	$234.56	$234.55	$234.60
7 purchase totals =	$668.50		$721.1197	$721.11	$721.10	$721.20