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	$87.55	10.476%	$96.7217	$96.72	$96.70	$96.70
Purchase #2	$150.97	5.741%	$159.6372	$159.64	$159.65	$159.60
Purchase #3	$105.37	12.851%	$118.9111	$118.91	$118.90	$118.90
Purchase #4	$138.64	13.676%	$157.6004	$157.60	$157.60	$157.60
Purchase #5	$207.47	7.132%	$222.2668	$222.27	$222.25	$222.30
Purchase #6	$171.89	4.502%	$179.6285	$179.63	$179.65	$179.60
Purchase #7	$146.96	8.498%	$159.4487	$159.45	$159.45	$159.40
7 purchase totals =	$1,008.85		$1,094.2144	$1,094.22	$1,094.20	$1,094.10