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	$200.91	3.680%	$208.3035	$208.30	$208.30	$208.30
Purchase #2	$131.30	13.548%	$149.0885	$149.09	$149.10	$149.10
Purchase #3	$198.62	12.185%	$222.8218	$222.82	$222.80	$222.80
Purchase #4	$63.99	5.289%	$67.3744	$67.37	$67.35	$67.40
Purchase #5	$68.84	5.336%	$72.5133	$72.51	$72.50	$72.50
Purchase #6	$190.63	10.621%	$210.8768	$210.88	$210.90	$210.90
Purchase #7	$121.49	4.445%	$126.8902	$126.89	$126.90	$126.90
7 purchase totals =	$975.78		$1,057.8685	$1,057.86	$1,057.85	$1,057.90