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	$174.74	11.827%	$195.4065	$195.41	$195.40	$195.40
Purchase #2	$185.41	12.478%	$208.5455	$208.55	$208.55	$208.50
Purchase #3	$108.57	13.297%	$123.0066	$123.01	$123.00	$123.00
Purchase #4	$58.80	11.410%	$65.5091	$65.51	$65.50	$65.50
Purchase #5	$39.53	10.336%	$43.6158	$43.62	$43.60	$43.60
Purchase #6	$84.53	4.481%	$88.3178	$88.32	$88.30	$88.30
Purchase #7	$93.95	4.320%	$98.0086	$98.01	$98.00	$98.00
7 purchase totals =	$745.53		$822.4099	$822.43	$822.35	$822.30