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	$105.58	6.423%	$112.3614	$112.36	$112.35	$112.40
Purchase #2	$22.36	6.838%	$23.889	$23.89	$23.90	$23.90
Purchase #3	$49.77	9.752%	$54.6236	$54.62	$54.60	$54.60
Purchase #4	$125.48	9.599%	$137.5248	$137.52	$137.50	$137.50
Purchase #5	$90.98	5.384%	$95.8784	$95.88	$95.90	$95.90
Purchase #6	$66.89	8.148%	$72.3402	$72.34	$72.35	$72.30
Purchase #7	$41.84	9.567%	$45.8428	$45.84	$45.85	$45.80
7 purchase totals =	$502.90		$542.4602	$542.45	$542.45	$542.40