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	$171.64	7.773%	$184.9816	$184.98	$185.00	$185.00
Purchase #2	$50.61	11.417%	$56.3881	$56.39	$56.40	$56.40
Purchase #3	$36.90	6.368%	$39.2498	$39.25	$39.25	$39.20
Purchase #4	$139.83	5.592%	$147.6493	$147.65	$147.65	$147.60
Purchase #5	$73.50	12.290%	$82.5332	$82.53	$82.55	$82.50
Purchase #6	$67.51	12.820%	$76.1648	$76.16	$76.15	$76.20
Purchase #7	$152.85	13.162%	$172.9681	$172.97	$172.95	$173.00
7 purchase totals =	$692.84		$759.9349	$759.93	$759.95	$759.90