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	$232.55	7.523%	$250.0447	$250.04	$250.05	$250.00
Purchase #2	$235.42	6.215%	$250.0514	$250.05	$250.05	$250.10
Purchase #3	$104.97	4.619%	$109.8186	$109.82	$109.80	$109.80
Purchase #4	$116.36	6.341%	$123.7384	$123.74	$123.75	$123.70
Purchase #5	$123.82	13.418%	$140.4342	$140.43	$140.45	$140.40
Purchase #6	$134.31	6.505%	$143.0469	$143.05	$143.05	$143.00
Purchase #7	$152.35	3.425%	$157.568	$157.57	$157.55	$157.60
7 purchase totals =	$1,099.78		$1,174.7022	$1,174.70	$1,174.70	$1,174.60