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	$67.52	5.367%	$71.1438	$71.14	$71.15	$71.10
Purchase #2	$6.51	12.711%	$7.3375	$7.34	$7.35	$7.30
Purchase #3	$112.37	9.308%	$122.8294	$122.83	$122.85	$122.80
Purchase #4	$199.54	11.825%	$223.1356	$223.14	$223.15	$223.10
Purchase #5	$96.34	9.479%	$105.4721	$105.47	$105.45	$105.50
Purchase #6	$172.58	3.186%	$178.0784	$178.08	$178.10	$178.10
Purchase #7	$189.58	12.549%	$213.3704	$213.37	$213.35	$213.40
7 purchase totals =	$844.44		$921.3672	$921.37	$921.40	$921.30