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	$173.96	3.857%	$180.6696	$180.67	$180.65	$180.70
Purchase #2	$164.33	5.728%	$173.7428	$173.74	$173.75	$173.70
Purchase #3	$178.83	3.689%	$185.427	$185.43	$185.45	$185.40
Purchase #4	$117.68	11.322%	$131.0037	$131.00	$131.00	$131.00
Purchase #5	$43.30	5.336%	$45.6105	$45.61	$45.60	$45.60
Purchase #6	$240.53	10.789%	$266.4808	$266.48	$266.50	$266.50
Purchase #7	$69.89	12.690%	$78.759	$78.76	$78.75	$78.80
7 purchase totals =	$988.52		$1,061.6934	$1,061.69	$1,061.70	$1,061.70