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	$44.46	3.335%	$45.9427	$45.94	$45.95	$45.90
Purchase #2	$153.68	13.121%	$173.8444	$173.84	$173.85	$173.80
Purchase #3	$94.96	5.703%	$100.3756	$100.38	$100.40	$100.40
Purchase #4	$136.73	13.154%	$154.7155	$154.72	$154.70	$154.70
Purchase #5	$9.39	12.570%	$10.5703	$10.57	$10.55	$10.60
Purchase #6	$86.88	13.111%	$98.2708	$98.27	$98.25	$98.30
Purchase #7	$159.27	13.868%	$181.3576	$181.36	$181.35	$181.40
7 purchase totals =	$685.37		$765.0769	$765.08	$765.05	$765.10