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	$227.54	9.109%	$248.2666	$248.27	$248.25	$248.30
Purchase #2	$90.83	13.319%	$102.9276	$102.93	$102.95	$102.90
Purchase #3	$192.28	6.112%	$204.0322	$204.03	$204.05	$204.00
Purchase #4	$19.87	9.247%	$21.7074	$21.71	$21.70	$21.70
Purchase #5	$62.96	3.841%	$65.3783	$65.38	$65.40	$65.40
Purchase #6	$73.44	7.378%	$78.8584	$78.86	$78.85	$78.90
Purchase #7	$34.64	13.598%	$39.3503	$39.35	$39.35	$39.40
7 purchase totals =	$701.56		$760.5208	$760.53	$760.55	$760.60