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	$234.81	3.715%	$243.5332	$243.53	$243.55	$243.50
Purchase #2	$221.28	10.751%	$245.0698	$245.07	$245.05	$245.10
Purchase #3	$159.76	6.794%	$170.6141	$170.61	$170.60	$170.60
Purchase #4	$183.42	7.372%	$196.9417	$196.94	$196.95	$196.90
Purchase #5	$107.87	6.630%	$115.0218	$115.02	$115.00	$115.00
Purchase #6	$151.52	7.536%	$162.9385	$162.94	$162.95	$162.90
Purchase #7	$40.77	11.613%	$45.5046	$45.50	$45.50	$45.50
7 purchase totals =	$1,099.43		$1,179.6237	$1,179.61	$1,179.60	$1,179.50