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	$78.72	13.611%	$89.4346	$89.43	$89.45	$89.40
Purchase #2	$84.37	12.543%	$94.9525	$94.95	$94.95	$95.00
Purchase #3	$152.79	10.469%	$168.7856	$168.79	$168.80	$168.80
Purchase #4	$234.56	9.705%	$257.324	$257.32	$257.30	$257.30
Purchase #5	$124.85	4.434%	$130.3858	$130.39	$130.40	$130.40
Purchase #6	$162.84	6.471%	$173.3774	$173.38	$173.40	$173.40
Purchase #7	$55.90	5.389%	$58.9125	$58.91	$58.90	$58.90
7 purchase totals =	$894.03		$973.1724	$973.17	$973.20	$973.20