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	$95.31	12.154%	$106.894	$106.89	$106.90	$106.90
Purchase #2	$75.59	4.195%	$78.761	$78.76	$78.75	$78.80
Purchase #3	$85.86	11.770%	$95.9657	$95.97	$95.95	$96.00
Purchase #4	$211.90	13.653%	$240.8307	$240.83	$240.85	$240.80
Purchase #5	$199.77	12.828%	$225.3965	$225.40	$225.40	$225.40
Purchase #6	$93.57	13.324%	$106.0373	$106.04	$106.05	$106.00
Purchase #7	$29.78	6.125%	$31.604	$31.60	$31.60	$31.60
7 purchase totals =	$791.78		$885.4892	$885.49	$885.50	$885.50