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	$121.72	3.735%	$126.2662	$126.27	$126.25	$126.30
Purchase #2	$53.98	4.685%	$56.509	$56.51	$56.50	$56.50
Purchase #3	$151.43	8.640%	$164.5136	$164.51	$164.50	$164.50
Purchase #4	$209.27	6.855%	$223.6155	$223.62	$223.60	$223.60
Purchase #5	$210.43	12.690%	$237.1336	$237.13	$237.15	$237.10
Purchase #6	$125.31	11.815%	$140.1154	$140.12	$140.10	$140.10
Purchase #7	$18.49	3.587%	$19.1532	$19.15	$19.15	$19.20
7 purchase totals =	$890.63		$967.3065	$967.31	$967.25	$967.30