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	$185.94	10.753%	$205.9341	$205.93	$205.95	$205.90
Purchase #2	$119.64	4.218%	$124.6864	$124.69	$124.70	$124.70
Purchase #3	$228.55	4.424%	$238.6611	$238.66	$238.65	$238.70
Purchase #4	$139.98	3.818%	$145.3244	$145.32	$145.30	$145.30
Purchase #5	$40.78	12.328%	$45.8074	$45.81	$45.80	$45.80
Purchase #6	$138.50	12.745%	$156.1518	$156.15	$156.15	$156.20
Purchase #7	$40.78	13.614%	$46.3318	$46.33	$46.35	$46.30
7 purchase totals =	$894.17		$962.8970	$962.89	$962.90	$962.90