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	$201.40	5.760%	$213.0006	$213.00	$213.00	$213.00
Purchase #2	$124.43	7.328%	$133.5482	$133.55	$133.55	$133.50
Purchase #3	$249.30	12.672%	$280.8913	$280.89	$280.90	$280.90
Purchase #4	$73.88	12.356%	$83.0086	$83.01	$83.00	$83.00
Purchase #5	$184.55	8.852%	$200.8864	$200.89	$200.90	$200.90
Purchase #6	$19.89	3.379%	$20.5621	$20.56	$20.55	$20.60
Purchase #7	$160.79	8.274%	$174.0938	$174.09	$174.10	$174.10
7 purchase totals =	$1,014.24		$1,105.9910	$1,105.99	$1,106.00	$1,106.00