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	$61.84	13.466%	$70.1674	$70.17	$70.15	$70.20
Purchase #2	$135.66	6.688%	$144.7329	$144.73	$144.75	$144.70
Purchase #3	$239.41	9.725%	$262.6926	$262.69	$262.70	$262.70
Purchase #4	$55.78	7.223%	$59.809	$59.81	$59.80	$59.80
Purchase #5	$240.86	10.792%	$266.8536	$266.85	$266.85	$266.90
Purchase #6	$222.53	4.820%	$233.2559	$233.26	$233.25	$233.30
Purchase #7	$164.40	9.254%	$179.6136	$179.61	$179.60	$179.60
7 purchase totals =	$1,120.48		$1,217.1250	$1,217.12	$1,217.10	$1,217.20