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	$131.62	11.606%	$146.8958	$146.90	$146.90	$146.90
Purchase #2	$76.68	5.657%	$81.0178	$81.02	$81.00	$81.00
Purchase #3	$155.66	12.309%	$174.8202	$174.82	$174.80	$174.80
Purchase #4	$100.32	11.511%	$111.8678	$111.87	$111.85	$111.90
Purchase #5	$45.57	8.737%	$49.5515	$49.55	$49.55	$49.60
Purchase #6	$213.77	11.751%	$238.8901	$238.89	$238.90	$238.90
Purchase #7	$187.31	3.453%	$193.7778	$193.78	$193.80	$193.80
7 purchase totals =	$910.93		$996.8210	$996.83	$996.80	$996.90