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	$180.85	8.611%	$196.423	$196.42	$196.40	$196.40
Purchase #2	$86.43	10.249%	$95.2882	$95.29	$95.30	$95.30
Purchase #3	$134.30	6.554%	$143.102	$143.10	$143.10	$143.10
Purchase #4	$135.63	6.385%	$144.29	$144.29	$144.30	$144.30
Purchase #5	$142.63	8.308%	$154.4797	$154.48	$154.50	$154.50
Purchase #6	$73.53	4.182%	$76.605	$76.61	$76.60	$76.60
Purchase #7	$79.37	13.673%	$90.2223	$90.22	$90.20	$90.20
7 purchase totals =	$832.74		$900.4102	$900.41	$900.40	$900.40