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	$217.92	7.421%	$234.0918	$234.09	$234.10	$234.10
Purchase #2	$25.86	5.736%	$27.3433	$27.34	$27.35	$27.30
Purchase #3	$15.59	11.300%	$17.3517	$17.35	$17.35	$17.40
Purchase #4	$67.89	5.115%	$71.3626	$71.36	$71.35	$71.40
Purchase #5	$171.30	8.842%	$186.4463	$186.45	$186.45	$186.40
Purchase #6	$126.60	11.508%	$141.1691	$141.17	$141.15	$141.20
Purchase #7	$197.98	12.549%	$222.8245	$222.82	$222.80	$222.80
7 purchase totals =	$823.14		$900.5893	$900.58	$900.55	$900.60