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	$179.62	9.626%	$196.9102	$196.91	$196.90	$196.90
Purchase #2	$247.66	5.616%	$261.5686	$261.57	$261.55	$261.60
Purchase #3	$198.76	8.613%	$215.8792	$215.88	$215.90	$215.90
Purchase #4	$27.63	12.348%	$31.0418	$31.04	$31.05	$31.00
Purchase #5	$61.87	5.563%	$65.3118	$65.31	$65.30	$65.30
Purchase #6	$106.77	12.735%	$120.3672	$120.37	$120.35	$120.40
Purchase #7	$10.30	5.748%	$10.892	$10.89	$10.90	$10.90
7 purchase totals =	$832.61		$901.9708	$901.97	$901.95	$902.00