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	$11.90	4.481%	$12.4332	$12.43	$12.45	$12.40
Purchase #2	$44.98	7.603%	$48.3998	$48.40	$48.40	$48.40
Purchase #3	$92.48	10.712%	$102.3865	$102.39	$102.40	$102.40
Purchase #4	$63.32	3.199%	$65.3456	$65.35	$65.35	$65.30
Purchase #5	$161.92	7.742%	$174.4558	$174.46	$174.45	$174.50
Purchase #6	$151.33	11.555%	$168.8162	$168.82	$168.80	$168.80
Purchase #7	$104.71	5.136%	$110.0879	$110.09	$110.10	$110.10
7 purchase totals =	$630.64		$681.9250	$681.94	$681.95	$681.90