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	$185.26	7.128%	$198.4653	$198.47	$198.45	$198.50
Purchase #2	$80.87	6.226%	$85.905	$85.91	$85.90	$85.90
Purchase #3	$63.69	13.159%	$72.071	$72.07	$72.05	$72.10
Purchase #4	$75.64	12.694%	$85.2417	$85.24	$85.25	$85.20
Purchase #5	$234.56	6.320%	$249.3842	$249.38	$249.40	$249.40
Purchase #6	$78.78	13.863%	$89.7013	$89.70	$89.70	$89.70
Purchase #7	$246.71	12.764%	$278.2001	$278.20	$278.20	$278.20
7 purchase totals =	$965.51		$1,058.9686	$1,058.97	$1,058.95	$1,059.00