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	$173.82	7.326%	$186.5541	$186.55	$186.55	$186.60
Purchase #2	$177.43	4.567%	$185.5332	$185.53	$185.55	$185.50
Purchase #3	$126.54	3.808%	$131.3586	$131.36	$131.35	$131.40
Purchase #4	$147.33	7.828%	$158.863	$158.86	$158.85	$158.90
Purchase #5	$240.62	6.623%	$256.5563	$256.56	$256.55	$256.60
Purchase #6	$64.33	3.531%	$66.6015	$66.60	$66.60	$66.60
Purchase #7	$218.78	6.400%	$232.7819	$232.78	$232.80	$232.80
7 purchase totals =	$1,148.85		$1,218.2486	$1,218.24	$1,218.25	$1,218.40