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	$102.49	8.688%	$111.3943	$111.39	$111.40	$111.40
Purchase #2	$198.85	12.119%	$222.9486	$222.95	$222.95	$222.90
Purchase #3	$69.53	5.549%	$73.3882	$73.39	$73.40	$73.40
Purchase #4	$192.42	7.622%	$207.0863	$207.09	$207.10	$207.10
Purchase #5	$66.34	9.571%	$72.6894	$72.69	$72.70	$72.70
Purchase #6	$139.94	12.667%	$157.6662	$157.67	$157.65	$157.70
Purchase #7	$115.73	10.850%	$128.2867	$128.29	$128.30	$128.30
7 purchase totals =	$885.30		$973.4597	$973.47	$973.50	$973.50