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	$104.67	6.655%	$111.6358	$111.64	$111.65	$111.60
Purchase #2	$202.82	4.863%	$212.6831	$212.68	$212.70	$212.70
Purchase #3	$185.33	5.804%	$196.0866	$196.09	$196.10	$196.10
Purchase #4	$41.77	7.446%	$44.8802	$44.88	$44.90	$44.90
Purchase #5	$202.78	6.130%	$215.2104	$215.21	$215.20	$215.20
Purchase #6	$71.56	10.138%	$78.8148	$78.81	$78.80	$78.80
Purchase #7	$101.67	11.517%	$113.3793	$113.38	$113.40	$113.40
7 purchase totals =	$910.60		$972.6902	$972.69	$972.75	$972.70