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	$228.79	6.403%	$243.4394	$243.44	$243.45	$243.40
Purchase #2	$51.68	6.140%	$54.8532	$54.85	$54.85	$54.90
Purchase #3	$195.31	9.269%	$213.4133	$213.41	$213.40	$213.40
Purchase #4	$241.46	6.800%	$257.8793	$257.88	$257.90	$257.90
Purchase #5	$157.74	13.824%	$179.546	$179.55	$179.55	$179.50
Purchase #6	$178.38	11.812%	$199.4502	$199.45	$199.45	$199.50
Purchase #7	$47.90	7.495%	$51.4901	$51.49	$51.50	$51.50
7 purchase totals =	$1,101.26		$1,200.0715	$1,200.07	$1,200.10	$1,200.10