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	$180.61	12.108%	$202.4783	$202.48	$202.50	$202.50
Purchase #2	$70.85	11.357%	$78.8964	$78.90	$78.90	$78.90
Purchase #3	$45.81	3.504%	$47.4152	$47.42	$47.40	$47.40
Purchase #4	$153.81	11.527%	$171.5397	$171.54	$171.55	$171.50
Purchase #5	$106.42	13.653%	$120.9495	$120.95	$120.95	$120.90
Purchase #6	$60.94	4.144%	$63.4654	$63.47	$63.45	$63.50
Purchase #7	$126.37	4.129%	$131.5878	$131.59	$131.60	$131.60
7 purchase totals =	$744.81		$816.3323	$816.35	$816.35	$816.30