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	$165.55	13.316%	$187.5946	$187.59	$187.60	$187.60
Purchase #2	$179.71	12.712%	$202.5547	$202.55	$202.55	$202.60
Purchase #3	$164.49	4.584%	$172.0302	$172.03	$172.05	$172.00
Purchase #4	$67.56	6.613%	$72.0277	$72.03	$72.05	$72.00
Purchase #5	$89.75	11.831%	$100.3683	$100.37	$100.35	$100.40
Purchase #6	$182.93	12.362%	$205.5438	$205.54	$205.55	$205.50
Purchase #7	$193.53	6.858%	$206.8023	$206.80	$206.80	$206.80
7 purchase totals =	$1,043.52		$1,146.9216	$1,146.91	$1,146.95	$1,146.90