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	$125.82	7.544%	$135.3119	$135.31	$135.30	$135.30
Purchase #2	$32.38	13.751%	$36.8326	$36.83	$36.85	$36.80
Purchase #3	$121.30	9.428%	$132.7362	$132.74	$132.75	$132.70
Purchase #4	$199.61	4.189%	$207.9717	$207.97	$207.95	$208.00
Purchase #5	$172.84	13.816%	$196.7196	$196.72	$196.70	$196.70
Purchase #6	$81.71	11.126%	$90.8011	$90.80	$90.80	$90.80
Purchase #7	$230.86	13.201%	$261.3358	$261.34	$261.35	$261.30
7 purchase totals =	$964.52		$1,061.7089	$1,061.71	$1,061.70	$1,061.60