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	$166.91	9.485%	$182.7414	$182.74	$182.75	$182.70
Purchase #2	$113.62	11.705%	$126.9192	$126.92	$126.90	$126.90
Purchase #3	$43.37	5.166%	$45.6105	$45.61	$45.60	$45.60
Purchase #4	$247.45	13.431%	$280.685	$280.69	$280.70	$280.70
Purchase #5	$75.31	7.566%	$81.008	$81.01	$81.00	$81.00
Purchase #6	$48.69	12.834%	$54.9389	$54.94	$54.95	$54.90
Purchase #7	$78.56	7.625%	$84.5502	$84.55	$84.55	$84.60
7 purchase totals =	$773.91		$856.4532	$856.46	$856.45	$856.40