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	$148.55	13.403%	$168.4602	$168.46	$168.45	$168.50
Purchase #2	$99.57	13.140%	$112.6535	$112.65	$112.65	$112.70
Purchase #3	$224.73	13.482%	$255.0281	$255.03	$255.05	$255.00
Purchase #4	$80.78	6.137%	$85.7375	$85.74	$85.75	$85.70
Purchase #5	$32.77	11.232%	$36.4507	$36.45	$36.45	$36.50
Purchase #6	$115.59	5.796%	$122.2896	$122.29	$122.30	$122.30
Purchase #7	$107.50	8.737%	$116.8923	$116.89	$116.90	$116.90
7 purchase totals =	$809.49		$897.5119	$897.51	$897.55	$897.60