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	$95.98	13.768%	$109.1945	$109.19	$109.20	$109.20
Purchase #2	$132.94	7.280%	$142.618	$142.62	$142.60	$142.60
Purchase #3	$222.40	6.465%	$236.7782	$236.78	$236.80	$236.80
Purchase #4	$92.29	10.127%	$101.6362	$101.64	$101.65	$101.60
Purchase #5	$82.61	9.663%	$90.5926	$90.59	$90.60	$90.60
Purchase #6	$21.82	7.874%	$23.5381	$23.54	$23.55	$23.50
Purchase #7	$27.76	4.778%	$29.0864	$29.09	$29.10	$29.10
7 purchase totals =	$675.80		$733.4440	$733.45	$733.50	$733.40