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	$123.64	13.130%	$139.8739	$139.87	$139.85	$139.90
Purchase #2	$34.97	3.266%	$36.1121	$36.11	$36.10	$36.10
Purchase #3	$38.25	13.655%	$43.473	$43.47	$43.45	$43.50
Purchase #4	$84.48	4.798%	$88.5334	$88.53	$88.55	$88.50
Purchase #5	$46.45	10.717%	$51.428	$51.43	$51.45	$51.40
Purchase #6	$208.44	6.846%	$222.7098	$222.71	$222.70	$222.70
Purchase #7	$68.98	5.745%	$72.9429	$72.94	$72.95	$72.90
7 purchase totals =	$605.21		$655.0731	$655.06	$655.05	$655.00