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	$54.38	3.143%	$56.0892	$56.09	$56.10	$56.10
Purchase #2	$105.58	5.153%	$111.0205	$111.02	$111.00	$111.00
Purchase #3	$174.56	12.438%	$196.2718	$196.27	$196.25	$196.30
Purchase #4	$20.49	7.817%	$22.0917	$22.09	$22.10	$22.10
Purchase #5	$134.48	4.111%	$140.0085	$140.01	$140.00	$140.00
Purchase #6	$207.52	12.409%	$233.2712	$233.27	$233.25	$233.30
Purchase #7	$25.61	7.703%	$27.5827	$27.58	$27.60	$27.60
7 purchase totals =	$722.62		$786.3356	$786.33	$786.30	$786.40