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	$161.59	4.857%	$169.4384	$169.44	$169.45	$169.40
Purchase #2	$34.47	7.720%	$37.1311	$37.13	$37.15	$37.10
Purchase #3	$132.92	5.386%	$140.0791	$140.08	$140.10	$140.10
Purchase #4	$119.74	9.529%	$131.15	$131.15	$131.15	$131.20
Purchase #5	$71.63	13.844%	$81.5465	$81.55	$81.55	$81.50
Purchase #6	$137.62	11.134%	$152.9426	$152.94	$152.95	$152.90
Purchase #7	$150.75	3.861%	$156.5705	$156.57	$156.55	$156.60
7 purchase totals =	$808.72		$868.8582	$868.86	$868.90	$868.80