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	$74.61	8.680%	$81.0861	$81.09	$81.10	$81.10
Purchase #2	$173.46	4.405%	$181.1009	$181.10	$181.10	$181.10
Purchase #3	$213.32	4.314%	$222.5226	$222.52	$222.50	$222.50
Purchase #4	$63.98	11.656%	$71.4375	$71.44	$71.45	$71.40
Purchase #5	$15.54	10.478%	$17.1683	$17.17	$17.15	$17.20
Purchase #6	$206.96	7.180%	$221.8197	$221.82	$221.80	$221.80
Purchase #7	$129.57	6.371%	$137.8249	$137.82	$137.80	$137.80
7 purchase totals =	$877.44		$932.9600	$932.96	$932.90	$932.90