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	$158.86	10.430%	$175.4291	$175.43	$175.45	$175.40
Purchase #2	$6.54	5.861%	$6.9233	$6.92	$6.90	$6.90
Purchase #3	$120.51	13.638%	$136.9452	$136.95	$136.95	$136.90
Purchase #4	$98.83	13.714%	$112.3835	$112.38	$112.40	$112.40
Purchase #5	$134.97	8.569%	$146.5356	$146.54	$146.55	$146.50
Purchase #6	$198.30	5.155%	$208.5224	$208.52	$208.50	$208.50
Purchase #7	$73.42	12.267%	$82.4264	$82.43	$82.45	$82.40
7 purchase totals =	$791.43		$869.1655	$869.17	$869.20	$869.00