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	$12.51	8.261%	$13.5435	$13.54	$13.55	$13.50
Purchase #2	$212.32	12.679%	$239.2401	$239.24	$239.25	$239.20
Purchase #3	$102.82	10.240%	$113.3488	$113.35	$113.35	$113.30
Purchase #4	$128.39	13.856%	$146.1797	$146.18	$146.20	$146.20
Purchase #5	$217.46	3.852%	$225.8366	$225.84	$225.85	$225.80
Purchase #6	$75.78	8.478%	$82.2046	$82.20	$82.20	$82.20
Purchase #7	$189.49	3.362%	$195.8607	$195.86	$195.85	$195.90
7 purchase totals =	$938.77		$1,016.2140	$1,016.21	$1,016.25	$1,016.10