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	$65.54	8.369%	$71.025	$71.03	$71.05	$71.00
Purchase #2	$176.46	8.645%	$191.715	$191.72	$191.70	$191.70
Purchase #3	$38.33	9.606%	$42.012	$42.01	$42.00	$42.00
Purchase #4	$122.71	9.844%	$134.7896	$134.79	$134.80	$134.80
Purchase #5	$241.69	9.777%	$265.32	$265.32	$265.30	$265.30
Purchase #6	$250.29	12.259%	$280.9731	$280.97	$280.95	$281.00
Purchase #7	$20.59	10.110%	$22.6716	$22.67	$22.65	$22.70
7 purchase totals =	$915.61		$1,008.5063	$1,008.51	$1,008.45	$1,008.50