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	$179.61	6.657%	$191.5666	$191.57	$191.55	$191.60
Purchase #2	$113.56	11.444%	$126.5558	$126.56	$126.55	$126.60
Purchase #3	$103.52	11.854%	$115.7913	$115.79	$115.80	$115.80
Purchase #4	$29.58	6.260%	$31.4317	$31.43	$31.45	$31.40
Purchase #5	$183.37	9.225%	$200.2859	$200.29	$200.30	$200.30
Purchase #6	$80.58	6.621%	$85.9152	$85.92	$85.90	$85.90
Purchase #7	$160.71	13.456%	$182.3351	$182.34	$182.35	$182.30
7 purchase totals =	$850.93		$933.8816	$933.90	$933.90	$933.90