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	$55.71	6.855%	$59.5289	$59.53	$59.55	$59.50
Purchase #2	$29.79	6.270%	$31.6578	$31.66	$31.65	$31.70
Purchase #3	$233.70	11.426%	$260.4026	$260.40	$260.40	$260.40
Purchase #4	$121.42	4.522%	$126.9106	$126.91	$126.90	$126.90
Purchase #5	$141.46	3.168%	$145.9415	$145.94	$145.95	$145.90
Purchase #6	$169.89	10.789%	$188.2194	$188.22	$188.20	$188.20
Purchase #7	$221.60	10.294%	$244.4115	$244.41	$244.40	$244.40
7 purchase totals =	$973.57		$1,057.0723	$1,057.07	$1,057.05	$1,057.00