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	$177.80	12.713%	$200.4037	$200.40	$200.40	$200.40
Purchase #2	$48.64	8.555%	$52.8012	$52.80	$52.80	$52.80
Purchase #3	$66.97	5.271%	$70.5	$70.50	$70.50	$70.50
Purchase #4	$250.53	6.326%	$266.3785	$266.38	$266.40	$266.40
Purchase #5	$207.33	8.705%	$225.3781	$225.38	$225.40	$225.40
Purchase #6	$204.94	9.272%	$223.942	$223.94	$223.95	$223.90
Purchase #7	$120.89	3.825%	$125.514	$125.51	$125.50	$125.50
7 purchase totals =	$1,077.10		$1,164.9175	$1,164.91	$1,164.95	$1,164.90