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	$60.30	8.342%	$65.3302	$65.33	$65.35	$65.30
Purchase #2	$200.49	6.468%	$213.4577	$213.46	$213.45	$213.50
Purchase #3	$177.77	7.358%	$190.8503	$190.85	$190.85	$190.90
Purchase #4	$157.76	4.430%	$164.7488	$164.75	$164.75	$164.70
Purchase #5	$180.68	9.605%	$198.0343	$198.03	$198.05	$198.00
Purchase #6	$117.45	5.123%	$123.467	$123.47	$123.45	$123.50
Purchase #7	$147.35	4.498%	$153.9778	$153.98	$154.00	$154.00
7 purchase totals =	$1,041.80		$1,109.8661	$1,109.87	$1,109.90	$1,109.90