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	$210.40	3.439%	$217.6357	$217.64	$217.65	$217.60
Purchase #2	$25.77	8.398%	$27.9342	$27.93	$27.95	$27.90
Purchase #3	$63.34	13.336%	$71.787	$71.79	$71.80	$71.80
Purchase #4	$143.87	10.396%	$158.8267	$158.83	$158.85	$158.80
Purchase #5	$89.31	6.698%	$95.292	$95.29	$95.30	$95.30
Purchase #6	$128.39	11.205%	$142.7761	$142.78	$142.80	$142.80
Purchase #7	$195.34	11.837%	$218.4624	$218.46	$218.45	$218.50
7 purchase totals =	$856.42		$932.7141	$932.72	$932.80	$932.70