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	$224.64	9.496%	$245.9718	$245.97	$245.95	$246.00
Purchase #2	$128.59	10.496%	$142.0868	$142.09	$142.10	$142.10
Purchase #3	$79.79	13.770%	$90.7771	$90.78	$90.80	$90.80
Purchase #4	$98.77	10.338%	$108.9808	$108.98	$109.00	$109.00
Purchase #5	$128.98	12.838%	$145.5385	$145.54	$145.55	$145.50
Purchase #6	$50.38	10.140%	$55.4885	$55.49	$55.50	$55.50
Purchase #7	$58.47	4.314%	$60.9924	$60.99	$61.00	$61.00
7 purchase totals =	$769.62		$849.8359	$849.84	$849.90	$849.90