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	$147.93	3.833%	$153.6002	$153.60	$153.60	$153.60
Purchase #2	$145.85	12.363%	$163.8814	$163.88	$163.90	$163.90
Purchase #3	$104.78	7.496%	$112.6343	$112.63	$112.65	$112.60
Purchase #4	$130.79	10.725%	$144.8172	$144.82	$144.80	$144.80
Purchase #5	$181.72	8.342%	$196.8791	$196.88	$196.90	$196.90
Purchase #6	$223.91	4.535%	$234.0643	$234.06	$234.05	$234.10
Purchase #7	$227.67	9.655%	$249.6515	$249.65	$249.65	$249.70
7 purchase totals =	$1,162.65		$1,255.5280	$1,255.52	$1,255.55	$1,255.60