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	$187.75	11.801%	$209.9064	$209.91	$209.90	$209.90
Purchase #2	$217.57	9.198%	$237.5821	$237.58	$237.60	$237.60
Purchase #3	$102.39	8.825%	$111.4259	$111.43	$111.45	$111.40
Purchase #4	$84.76	13.307%	$96.039	$96.04	$96.05	$96.00
Purchase #5	$187.78	11.256%	$208.9165	$208.92	$208.90	$208.90
Purchase #6	$139.92	12.196%	$156.9846	$156.98	$157.00	$157.00
Purchase #7	$221.73	10.749%	$245.5638	$245.56	$245.55	$245.60
7 purchase totals =	$1,141.90		$1,266.4183	$1,266.42	$1,266.45	$1,266.40