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	$249.42	13.258%	$282.4881	$282.49	$282.50	$282.50
Purchase #2	$6.78	13.435%	$7.6909	$7.69	$7.70	$7.70
Purchase #3	$92.85	7.225%	$99.5584	$99.56	$99.55	$99.60
Purchase #4	$209.56	3.776%	$217.473	$217.47	$217.45	$217.50
Purchase #5	$53.96	4.508%	$56.3925	$56.39	$56.40	$56.40
Purchase #6	$241.87	9.589%	$265.0629	$265.06	$265.05	$265.10
Purchase #7	$7.58	4.224%	$7.9002	$7.90	$7.90	$7.90
7 purchase totals =	$862.02		$936.5660	$936.56	$936.55	$936.70