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	$131.35	8.660%	$142.7249	$142.72	$142.70	$142.70
Purchase #2	$249.87	4.440%	$260.9642	$260.96	$260.95	$261.00
Purchase #3	$28.97	8.826%	$31.5269	$31.53	$31.55	$31.50
Purchase #4	$186.95	9.762%	$205.2001	$205.20	$205.20	$205.20
Purchase #5	$84.43	5.524%	$89.0939	$89.09	$89.10	$89.10
Purchase #6	$94.86	5.116%	$99.713	$99.71	$99.70	$99.70
Purchase #7	$215.89	11.747%	$241.2506	$241.25	$241.25	$241.30
7 purchase totals =	$992.32		$1,070.4736	$1,070.46	$1,070.45	$1,070.50