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	$130.89	8.468%	$141.9738	$141.97	$141.95	$142.00
Purchase #2	$174.60	12.481%	$196.3918	$196.39	$196.40	$196.40
Purchase #3	$149.50	5.247%	$157.3443	$157.34	$157.35	$157.30
Purchase #4	$66.60	9.338%	$72.8191	$72.82	$72.80	$72.80
Purchase #5	$236.57	8.516%	$256.7163	$256.72	$256.70	$256.70
Purchase #6	$153.97	8.128%	$166.4847	$166.48	$166.50	$166.50
Purchase #7	$104.73	11.846%	$117.1363	$117.14	$117.15	$117.10
7 purchase totals =	$1,016.86		$1,108.8663	$1,108.86	$1,108.85	$1,108.80