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	$54.81	7.799%	$59.0846	$59.08	$59.10	$59.10
Purchase #2	$196.97	6.215%	$209.2117	$209.21	$209.20	$209.20
Purchase #3	$203.45	3.278%	$210.1191	$210.12	$210.10	$210.10
Purchase #4	$167.46	8.259%	$181.2905	$181.29	$181.30	$181.30
Purchase #5	$52.42	11.762%	$58.5856	$58.59	$58.60	$58.60
Purchase #6	$93.99	6.215%	$99.8315	$99.83	$99.85	$99.80
Purchase #7	$38.56	10.141%	$42.4704	$42.47	$42.45	$42.50
7 purchase totals =	$807.66		$860.5934	$860.59	$860.60	$860.60