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	$165.82	3.512%	$171.6436	$171.64	$171.65	$171.60
Purchase #2	$92.31	12.150%	$103.5257	$103.53	$103.55	$103.50
Purchase #3	$179.36	6.340%	$190.7314	$190.73	$190.75	$190.70
Purchase #4	$182.35	3.257%	$188.2891	$188.29	$188.30	$188.30
Purchase #5	$88.38	13.680%	$100.4704	$100.47	$100.45	$100.50
Purchase #6	$136.45	9.602%	$149.5519	$149.55	$149.55	$149.60
Purchase #7	$39.46	10.203%	$43.4861	$43.49	$43.50	$43.50
7 purchase totals =	$884.13		$947.6982	$947.70	$947.75	$947.70