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	$228.39	9.708%	$250.5621	$250.56	$250.55	$250.60
Purchase #2	$37.51	12.177%	$42.0776	$42.08	$42.10	$42.10
Purchase #3	$184.79	11.565%	$206.161	$206.16	$206.15	$206.20
Purchase #4	$80.79	3.270%	$83.4318	$83.43	$83.45	$83.40
Purchase #5	$107.93	3.508%	$111.7162	$111.72	$111.70	$111.70
Purchase #6	$184.77	3.193%	$190.6697	$190.67	$190.65	$190.70
Purchase #7	$212.26	10.399%	$234.3329	$234.33	$234.35	$234.30
7 purchase totals =	$1,036.44		$1,118.9513	$1,118.95	$1,118.95	$1,119.00