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	$206.49	13.836%	$235.06	$235.06	$235.05	$235.10
Purchase #2	$102.71	9.462%	$112.4284	$112.43	$112.45	$112.40
Purchase #3	$80.93	10.635%	$89.5369	$89.54	$89.55	$89.50
Purchase #4	$83.67	5.264%	$88.0744	$88.07	$88.05	$88.10
Purchase #5	$142.68	5.367%	$150.3376	$150.34	$150.35	$150.30
Purchase #6	$195.30	6.795%	$208.5706	$208.57	$208.55	$208.60
Purchase #7	$109.43	10.511%	$120.9322	$120.93	$120.95	$120.90
7 purchase totals =	$921.21		$1,004.9401	$1,004.94	$1,004.95	$1,004.90