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	$176.65	5.564%	$186.4788	$186.48	$186.50	$186.50
Purchase #2	$33.79	11.444%	$37.6569	$37.66	$37.65	$37.70
Purchase #3	$134.73	10.466%	$148.8308	$148.83	$148.85	$148.80
Purchase #4	$151.51	10.814%	$167.8943	$167.89	$167.90	$167.90
Purchase #5	$154.50	6.591%	$164.6831	$164.68	$164.70	$164.70
Purchase #6	$198.77	9.309%	$217.2735	$217.27	$217.25	$217.30
Purchase #7	$104.36	12.478%	$117.382	$117.38	$117.40	$117.40
7 purchase totals =	$954.31		$1,040.1994	$1,040.19	$1,040.25	$1,040.30