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	$62.48	8.684%	$67.9058	$67.91	$67.90	$67.90
Purchase #2	$175.32	11.659%	$195.7606	$195.76	$195.75	$195.80
Purchase #3	$47.63	7.627%	$51.2627	$51.26	$51.25	$51.30
Purchase #4	$72.80	13.607%	$82.7059	$82.71	$82.70	$82.70
Purchase #5	$25.85	11.687%	$28.8711	$28.87	$28.85	$28.90
Purchase #6	$86.44	10.765%	$95.7453	$95.75	$95.75	$95.70
Purchase #7	$35.89	7.188%	$38.4698	$38.47	$38.45	$38.50
7 purchase totals =	$506.41		$560.7212	$560.73	$560.65	$560.80