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	$183.25	3.654%	$189.946	$189.95	$189.95	$189.90
Purchase #2	$249.65	9.786%	$274.0807	$274.08	$274.10	$274.10
Purchase #3	$144.43	10.234%	$159.211	$159.21	$159.20	$159.20
Purchase #4	$167.54	12.333%	$188.2027	$188.20	$188.20	$188.20
Purchase #5	$140.43	3.124%	$144.817	$144.82	$144.80	$144.80
Purchase #6	$27.25	3.724%	$28.2648	$28.26	$28.25	$28.30
Purchase #7	$89.36	12.531%	$100.5577	$100.56	$100.55	$100.60
7 purchase totals =	$1,001.91		$1,085.0799	$1,085.08	$1,085.05	$1,085.10