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	$84.49	11.270%	$94.012	$94.01	$94.00	$94.00
Purchase #2	$229.69	13.178%	$259.9585	$259.96	$259.95	$260.00
Purchase #3	$213.96	11.863%	$239.3421	$239.34	$239.35	$239.30
Purchase #4	$244.31	12.472%	$274.7803	$274.78	$274.80	$274.80
Purchase #5	$38.75	4.577%	$40.5236	$40.52	$40.50	$40.50
Purchase #6	$18.64	10.771%	$20.6477	$20.65	$20.65	$20.60
Purchase #7	$181.76	6.819%	$194.1542	$194.15	$194.15	$194.20
7 purchase totals =	$1,011.60		$1,123.4184	$1,123.41	$1,123.40	$1,123.40