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	$244.75	12.208%	$274.6291	$274.63	$274.65	$274.60
Purchase #2	$191.71	7.157%	$205.4307	$205.43	$205.45	$205.40
Purchase #3	$134.45	5.239%	$141.4938	$141.49	$141.50	$141.50
Purchase #4	$66.55	3.158%	$68.6516	$68.65	$68.65	$68.70
Purchase #5	$155.61	5.654%	$164.4082	$164.41	$164.40	$164.40
Purchase #6	$133.77	5.584%	$141.2397	$141.24	$141.25	$141.20
Purchase #7	$103.90	5.311%	$109.4181	$109.42	$109.40	$109.40
7 purchase totals =	$1,030.74		$1,105.2712	$1,105.27	$1,105.30	$1,105.20