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	$220.61	3.172%	$227.6077	$227.61	$227.60	$227.60
Purchase #2	$63.29	13.671%	$71.9424	$71.94	$71.95	$71.90
Purchase #3	$123.50	10.450%	$136.4058	$136.41	$136.40	$136.40
Purchase #4	$35.96	12.532%	$40.4665	$40.47	$40.45	$40.50
Purchase #5	$125.89	8.631%	$136.7556	$136.76	$136.75	$136.80
Purchase #6	$248.71	7.782%	$268.0646	$268.06	$268.05	$268.10
Purchase #7	$98.48	5.404%	$103.8019	$103.80	$103.80	$103.80
7 purchase totals =	$916.44		$985.0445	$985.05	$985.00	$985.10