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	$201.78	10.377%	$222.7187	$222.72	$222.70	$222.70
Purchase #2	$207.43	5.506%	$218.8511	$218.85	$218.85	$218.90
Purchase #3	$125.61	10.279%	$138.5215	$138.52	$138.50	$138.50
Purchase #4	$76.68	11.388%	$85.4123	$85.41	$85.40	$85.40
Purchase #5	$112.41	3.228%	$116.0386	$116.04	$116.05	$116.00
Purchase #6	$170.58	7.534%	$183.4315	$183.43	$183.45	$183.40
Purchase #7	$97.92	11.827%	$109.501	$109.50	$109.50	$109.50
7 purchase totals =	$992.41		$1,074.4747	$1,074.47	$1,074.45	$1,074.40