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	$213.88	6.853%	$228.5372	$228.54	$228.55	$228.50
Purchase #2	$139.76	3.478%	$144.6209	$144.62	$144.60	$144.60
Purchase #3	$159.33	5.300%	$167.7745	$167.77	$167.75	$167.80
Purchase #4	$180.48	6.171%	$191.6174	$191.62	$191.60	$191.60
Purchase #5	$25.39	12.222%	$28.4932	$28.49	$28.50	$28.50
Purchase #6	$153.37	11.789%	$171.4508	$171.45	$171.45	$171.50
Purchase #7	$79.97	5.602%	$84.4499	$84.45	$84.45	$84.40
7 purchase totals =	$952.18		$1,016.9439	$1,016.94	$1,016.90	$1,016.90