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	$121.77	7.802%	$131.2705	$131.27	$131.25	$131.30
Purchase #2	$57.58	13.569%	$65.393	$65.39	$65.40	$65.40
Purchase #3	$114.36	3.127%	$117.936	$117.94	$117.95	$117.90
Purchase #4	$226.54	6.552%	$241.3829	$241.38	$241.40	$241.40
Purchase #5	$150.67	6.491%	$160.45	$160.45	$160.45	$160.50
Purchase #6	$50.70	8.291%	$54.9035	$54.90	$54.90	$54.90
Purchase #7	$37.73	9.760%	$41.4124	$41.41	$41.40	$41.40
7 purchase totals =	$759.35		$812.7483	$812.74	$812.75	$812.80