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	$147.58	8.824%	$160.6025	$160.60	$160.60	$160.60
Purchase #2	$78.78	3.628%	$81.6381	$81.64	$81.65	$81.60
Purchase #3	$191.56	4.832%	$200.8162	$200.82	$200.80	$200.80
Purchase #4	$24.51	4.307%	$25.5656	$25.57	$25.55	$25.60
Purchase #5	$86.67	3.364%	$89.5856	$89.59	$89.60	$89.60
Purchase #6	$77.96	8.571%	$84.642	$84.64	$84.65	$84.60
Purchase #7	$184.63	13.147%	$208.9033	$208.90	$208.90	$208.90
7 purchase totals =	$791.69		$851.7533	$851.76	$851.75	$851.70