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	$243.47	9.405%	$266.3684	$266.37	$266.35	$266.40
Purchase #2	$166.89	3.630%	$172.9481	$172.95	$172.95	$172.90
Purchase #3	$90.39	6.461%	$96.2301	$96.23	$96.25	$96.20
Purchase #4	$42.96	8.140%	$46.4569	$46.46	$46.45	$46.50
Purchase #5	$187.80	11.492%	$209.382	$209.38	$209.40	$209.40
Purchase #6	$129.41	11.238%	$143.9531	$143.95	$143.95	$144.00
Purchase #7	$212.79	12.361%	$239.093	$239.09	$239.10	$239.10
7 purchase totals =	$1,073.71		$1,174.4316	$1,174.43	$1,174.45	$1,174.50