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	$125.83	5.720%	$133.0275	$133.03	$133.05	$133.00
Purchase #2	$183.37	7.297%	$196.7505	$196.75	$196.75	$196.80
Purchase #3	$238.72	13.338%	$270.5605	$270.56	$270.55	$270.60
Purchase #4	$185.83	11.831%	$207.8155	$207.82	$207.80	$207.80
Purchase #5	$61.91	6.476%	$65.9193	$65.92	$65.90	$65.90
Purchase #6	$143.47	8.743%	$156.0136	$156.01	$156.00	$156.00
Purchase #7	$238.43	13.769%	$271.2594	$271.26	$271.25	$271.30
7 purchase totals =	$1,177.56		$1,301.3463	$1,301.35	$1,301.30	$1,301.40