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	$246.46	13.803%	$280.4789	$280.48	$280.50	$280.50
Purchase #2	$174.47	4.746%	$182.7503	$182.75	$182.75	$182.80
Purchase #3	$67.45	12.582%	$75.9366	$75.94	$75.95	$75.90
Purchase #4	$119.33	9.789%	$131.0112	$131.01	$131.00	$131.00
Purchase #5	$152.36	10.410%	$168.2207	$168.22	$168.20	$168.20
Purchase #6	$139.70	9.811%	$153.406	$153.41	$153.40	$153.40
Purchase #7	$101.49	10.364%	$112.0084	$112.01	$112.00	$112.00
7 purchase totals =	$1,001.26		$1,103.8121	$1,103.82	$1,103.80	$1,103.80