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	$211.61	13.640%	$240.4736	$240.47	$240.45	$240.50
Purchase #2	$194.72	10.502%	$215.1695	$215.17	$215.15	$215.20
Purchase #3	$241.50	6.257%	$256.6107	$256.61	$256.60	$256.60
Purchase #4	$67.51	6.424%	$71.8468	$71.85	$71.85	$71.80
Purchase #5	$105.61	3.583%	$109.394	$109.39	$109.40	$109.40
Purchase #6	$6.25	3.164%	$6.4478	$6.45	$6.45	$6.40
Purchase #7	$29.46	8.576%	$31.9865	$31.99	$32.00	$32.00
7 purchase totals =	$856.66		$931.9289	$931.93	$931.90	$931.90