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	$210.86	11.570%	$235.2565	$235.26	$235.25	$235.30
Purchase #2	$247.70	13.402%	$280.8968	$280.90	$280.90	$280.90
Purchase #3	$133.56	7.681%	$143.8187	$143.82	$143.80	$143.80
Purchase #4	$238.95	6.144%	$253.6311	$253.63	$253.65	$253.60
Purchase #5	$169.54	12.811%	$191.2598	$191.26	$191.25	$191.30
Purchase #6	$167.68	13.821%	$190.8551	$190.86	$190.85	$190.90
Purchase #7	$85.29	8.748%	$92.7512	$92.75	$92.75	$92.80
7 purchase totals =	$1,253.58		$1,388.4692	$1,388.48	$1,388.45	$1,388.60