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	$177.59	5.822%	$187.9293	$187.93	$187.95	$187.90
Purchase #2	$142.73	6.833%	$152.4827	$152.48	$152.50	$152.50
Purchase #3	$146.62	13.142%	$165.8888	$165.89	$165.90	$165.90
Purchase #4	$90.86	13.754%	$103.3569	$103.36	$103.35	$103.40
Purchase #5	$155.46	5.756%	$164.4083	$164.41	$164.40	$164.40
Purchase #6	$98.48	3.800%	$102.2222	$102.22	$102.20	$102.20
Purchase #7	$58.39	10.576%	$64.5653	$64.57	$64.55	$64.60
7 purchase totals =	$870.13		$940.8535	$940.86	$940.85	$940.90