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	$140.37	9.201%	$153.2854	$153.29	$153.30	$153.30
Purchase #2	$197.57	5.782%	$208.9935	$208.99	$209.00	$209.00
Purchase #3	$111.72	3.399%	$115.5174	$115.52	$115.50	$115.50
Purchase #4	$246.40	8.362%	$267.004	$267.00	$267.00	$267.00
Purchase #5	$154.45	11.315%	$171.926	$171.93	$171.95	$171.90
Purchase #6	$72.59	7.800%	$78.252	$78.25	$78.25	$78.30
Purchase #7	$105.85	11.385%	$117.901	$117.90	$117.90	$117.90
7 purchase totals =	$1,028.95		$1,112.8793	$1,112.88	$1,112.90	$1,112.90