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	$90.94	8.414%	$98.5917	$98.59	$98.60	$98.60
Purchase #2	$47.32	11.141%	$52.5919	$52.59	$52.60	$52.60
Purchase #3	$75.39	13.684%	$85.7064	$85.71	$85.70	$85.70
Purchase #4	$116.29	13.385%	$131.8554	$131.86	$131.85	$131.90
Purchase #5	$181.69	5.326%	$191.3668	$191.37	$191.35	$191.40
Purchase #6	$183.25	12.844%	$206.7866	$206.79	$206.80	$206.80
Purchase #7	$200.54	13.699%	$228.012	$228.01	$228.00	$228.00
7 purchase totals =	$895.42		$994.9108	$994.92	$994.90	$995.00