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	$85.83	5.822%	$90.827	$90.83	$90.85	$90.80
Purchase #2	$112.53	3.497%	$116.4652	$116.47	$116.45	$116.50
Purchase #3	$139.48	12.491%	$156.9024	$156.90	$156.90	$156.90
Purchase #4	$250.63	11.187%	$278.668	$278.67	$278.65	$278.70
Purchase #5	$162.27	5.186%	$170.6853	$170.69	$170.70	$170.70
Purchase #6	$14.43	11.874%	$16.1434	$16.14	$16.15	$16.10
Purchase #7	$192.31	4.337%	$200.6505	$200.65	$200.65	$200.70
7 purchase totals =	$957.48		$1,030.3418	$1,030.35	$1,030.35	$1,030.40