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	$82.37	8.818%	$89.6334	$89.63	$89.65	$89.60
Purchase #2	$71.78	12.194%	$80.5329	$80.53	$80.55	$80.50
Purchase #3	$228.48	5.798%	$241.7273	$241.73	$241.75	$241.70
Purchase #4	$127.63	10.752%	$141.3528	$141.35	$141.35	$141.40
Purchase #5	$67.45	7.515%	$72.5189	$72.52	$72.50	$72.50
Purchase #6	$210.33	10.357%	$232.1139	$232.11	$232.10	$232.10
Purchase #7	$86.98	3.152%	$89.7216	$89.72	$89.70	$89.70
7 purchase totals =	$875.02		$947.6008	$947.59	$947.60	$947.50