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	$171.26	8.480%	$185.7828	$185.78	$185.80	$185.80
Purchase #2	$205.25	5.807%	$217.1689	$217.17	$217.15	$217.20
Purchase #3	$185.59	10.665%	$205.3832	$205.38	$205.40	$205.40
Purchase #4	$183.72	13.231%	$208.028	$208.03	$208.05	$208.00
Purchase #5	$196.85	12.858%	$222.161	$222.16	$222.15	$222.20
Purchase #6	$32.55	4.184%	$33.9119	$33.91	$33.90	$33.90
Purchase #7	$54.29	12.799%	$61.2386	$61.24	$61.25	$61.20
7 purchase totals =	$1,029.51		$1,133.6744	$1,133.67	$1,133.70	$1,133.70