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	$82.36	12.418%	$92.5875	$92.59	$92.60	$92.60
Purchase #2	$210.83	10.821%	$233.6439	$233.64	$233.65	$233.60
Purchase #3	$164.38	12.773%	$185.3763	$185.38	$185.40	$185.40
Purchase #4	$201.66	3.716%	$209.1537	$209.15	$209.15	$209.20
Purchase #5	$30.25	9.150%	$33.0179	$33.02	$33.00	$33.00
Purchase #6	$6.73	6.677%	$7.1794	$7.18	$7.20	$7.20
Purchase #7	$62.58	8.552%	$67.9318	$67.93	$67.95	$67.90
7 purchase totals =	$758.79		$828.8905	$828.89	$828.95	$828.90