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	$11.73	10.605%	$12.974	$12.97	$12.95	$13.00
Purchase #2	$197.32	12.838%	$222.6519	$222.65	$222.65	$222.70
Purchase #3	$81.89	11.591%	$91.3819	$91.38	$91.40	$91.40
Purchase #4	$196.32	7.373%	$210.7947	$210.79	$210.80	$210.80
Purchase #5	$244.43	6.801%	$261.0537	$261.05	$261.05	$261.10
Purchase #6	$129.57	8.800%	$140.9722	$140.97	$140.95	$141.00
Purchase #7	$114.57	7.595%	$123.2716	$123.27	$123.25	$123.30
7 purchase totals =	$975.83		$1,063.1000	$1,063.08	$1,063.05	$1,063.30