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	$140.55	3.803%	$145.8951	$145.90	$145.90	$145.90
Purchase #2	$34.96	13.348%	$39.6265	$39.63	$39.65	$39.60
Purchase #3	$174.48	9.684%	$191.3766	$191.38	$191.40	$191.40
Purchase #4	$22.90	4.227%	$23.868	$23.87	$23.85	$23.90
Purchase #5	$48.81	10.355%	$53.8643	$53.86	$53.85	$53.90
Purchase #6	$137.39	13.853%	$156.4226	$156.42	$156.40	$156.40
Purchase #7	$128.73	6.314%	$136.858	$136.86	$136.85	$136.90
7 purchase totals =	$687.82		$747.9111	$747.92	$747.90	$748.00