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	$67.99	5.799%	$71.9327	$71.93	$71.95	$71.90
Purchase #2	$167.96	6.637%	$179.1075	$179.11	$179.10	$179.10
Purchase #3	$123.51	7.406%	$132.6572	$132.66	$132.65	$132.70
Purchase #4	$52.43	6.591%	$55.8857	$55.89	$55.90	$55.90
Purchase #5	$168.52	10.725%	$186.5938	$186.59	$186.60	$186.60
Purchase #6	$114.54	8.606%	$124.3973	$124.40	$124.40	$124.40
Purchase #7	$127.35	12.245%	$142.944	$142.94	$142.95	$142.90
7 purchase totals =	$822.30		$893.5182	$893.52	$893.55	$893.50