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	$208.78	8.473%	$226.4699	$226.47	$226.45	$226.50
Purchase #2	$220.64	5.655%	$233.1172	$233.12	$233.10	$233.10
Purchase #3	$52.32	8.676%	$56.8593	$56.86	$56.85	$56.90
Purchase #4	$87.67	3.185%	$90.4623	$90.46	$90.45	$90.50
Purchase #5	$135.78	11.484%	$151.373	$151.37	$151.35	$151.40
Purchase #6	$60.38	9.746%	$66.2646	$66.26	$66.25	$66.30
Purchase #7	$94.76	5.576%	$100.0438	$100.04	$100.05	$100.00
7 purchase totals =	$860.33		$924.5901	$924.58	$924.50	$924.70