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	$139.63	10.354%	$154.0873	$154.09	$154.10	$154.10
Purchase #2	$39.44	10.214%	$43.4684	$43.47	$43.45	$43.50
Purchase #3	$112.45	13.385%	$127.5014	$127.50	$127.50	$127.50
Purchase #4	$145.99	9.521%	$159.8897	$159.89	$159.90	$159.90
Purchase #5	$71.64	10.262%	$78.9917	$78.99	$79.00	$79.00
Purchase #6	$243.51	13.531%	$276.4593	$276.46	$276.45	$276.50
Purchase #7	$92.78	12.734%	$104.5946	$104.59	$104.60	$104.60
7 purchase totals =	$845.44		$944.9924	$944.99	$945.00	$945.10