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	$106.71	4.348%	$111.3498	$111.35	$111.35	$111.30
Purchase #2	$8.33	7.118%	$8.9229	$8.92	$8.90	$8.90
Purchase #3	$210.43	5.862%	$222.7654	$222.77	$222.75	$222.80
Purchase #4	$12.64	5.497%	$13.3348	$13.33	$13.35	$13.30
Purchase #5	$43.64	4.277%	$45.5065	$45.51	$45.50	$45.50
Purchase #6	$229.81	11.866%	$257.0793	$257.08	$257.10	$257.10
Purchase #7	$225.94	9.118%	$246.5412	$246.54	$246.55	$246.50
7 purchase totals =	$837.50		$905.4999	$905.50	$905.50	$905.40