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	$138.41	6.179%	$146.9624	$146.96	$146.95	$147.00
Purchase #2	$101.35	7.725%	$109.1793	$109.18	$109.20	$109.20
Purchase #3	$148.43	9.151%	$162.0128	$162.01	$162.00	$162.00
Purchase #4	$109.85	12.389%	$123.4593	$123.46	$123.45	$123.50
Purchase #5	$205.97	9.364%	$225.257	$225.26	$225.25	$225.30
Purchase #6	$112.31	5.557%	$118.5511	$118.55	$118.55	$118.60
Purchase #7	$124.90	5.514%	$131.787	$131.79	$131.80	$131.80
7 purchase totals =	$941.22		$1,017.2089	$1,017.21	$1,017.20	$1,017.40