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	$250.25	4.339%	$261.1083	$261.11	$261.10	$261.10
Purchase #2	$116.49	9.438%	$127.4843	$127.48	$127.50	$127.50
Purchase #3	$164.42	7.335%	$176.4802	$176.48	$176.50	$176.50
Purchase #4	$29.66	12.769%	$33.4473	$33.45	$33.45	$33.40
Purchase #5	$113.61	12.558%	$127.8771	$127.88	$127.90	$127.90
Purchase #6	$77.37	3.325%	$79.9426	$79.94	$79.95	$79.90
Purchase #7	$148.62	13.792%	$169.1177	$169.12	$169.10	$169.10
7 purchase totals =	$900.42		$975.4575	$975.46	$975.50	$975.40