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	$47.61	7.861%	$51.3526	$51.35	$51.35	$51.40
Purchase #2	$19.70	11.275%	$21.9212	$21.92	$21.90	$21.90
Purchase #3	$229.37	11.591%	$255.9563	$255.96	$255.95	$256.00
Purchase #4	$38.70	11.826%	$43.2767	$43.28	$43.30	$43.30
Purchase #5	$248.35	9.744%	$272.5492	$272.55	$272.55	$272.50
Purchase #6	$120.69	9.275%	$131.884	$131.88	$131.90	$131.90
Purchase #7	$176.25	7.128%	$188.8131	$188.81	$188.80	$188.80
7 purchase totals =	$880.67		$965.7531	$965.75	$965.75	$965.80