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	$217.34	6.583%	$231.6475	$231.65	$231.65	$231.60
Purchase #2	$53.33	9.699%	$58.5025	$58.50	$58.50	$58.50
Purchase #3	$246.55	10.588%	$272.6547	$272.65	$272.65	$272.70
Purchase #4	$98.87	11.661%	$110.3992	$110.40	$110.40	$110.40
Purchase #5	$76.76	12.848%	$86.6221	$86.62	$86.60	$86.60
Purchase #6	$198.77	13.688%	$225.9776	$225.98	$226.00	$226.00
Purchase #7	$89.88	11.798%	$100.484	$100.48	$100.50	$100.50
7 purchase totals =	$981.50		$1,086.2876	$1,086.28	$1,086.30	$1,086.30