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	$208.77	6.632%	$222.6156	$222.62	$222.60	$222.60
Purchase #2	$41.43	10.242%	$45.6733	$45.67	$45.65	$45.70
Purchase #3	$231.58	5.284%	$243.8167	$243.82	$243.80	$243.80
Purchase #4	$92.33	10.103%	$101.6581	$101.66	$101.65	$101.70
Purchase #5	$40.96	6.364%	$43.5667	$43.57	$43.55	$43.60
Purchase #6	$182.51	11.651%	$203.7742	$203.77	$203.75	$203.80
Purchase #7	$212.29	11.846%	$237.4379	$237.44	$237.45	$237.40
7 purchase totals =	$1,009.87		$1,098.5425	$1,098.55	$1,098.45	$1,098.60