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	$13.85	8.705%	$15.0556	$15.06	$15.05	$15.10
Purchase #2	$131.87	7.725%	$142.057	$142.06	$142.05	$142.10
Purchase #3	$95.90	5.163%	$100.8513	$100.85	$100.85	$100.90
Purchase #4	$7.88	8.407%	$8.5425	$8.54	$8.55	$8.50
Purchase #5	$14.99	8.792%	$16.3079	$16.31	$16.30	$16.30
Purchase #6	$144.89	7.344%	$155.5307	$155.53	$155.55	$155.50
Purchase #7	$151.51	7.305%	$162.5778	$162.58	$162.60	$162.60
7 purchase totals =	$560.89		$600.9228	$600.93	$600.95	$601.00