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	$185.35	3.229%	$191.335	$191.34	$191.35	$191.30
Purchase #2	$141.96	10.299%	$156.5805	$156.58	$156.60	$156.60
Purchase #3	$94.67	4.121%	$98.5714	$98.57	$98.55	$98.60
Purchase #4	$185.89	11.291%	$206.8788	$206.88	$206.90	$206.90
Purchase #5	$215.59	4.441%	$225.1644	$225.16	$225.15	$225.20
Purchase #6	$38.27	7.362%	$41.0874	$41.09	$41.10	$41.10
Purchase #7	$213.47	5.476%	$225.1596	$225.16	$225.15	$225.20
7 purchase totals =	$1,075.20		$1,144.7771	$1,144.78	$1,144.80	$1,144.90