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	$40.82	4.565%	$42.6834	$42.68	$42.70	$42.70
Purchase #2	$180.79	5.122%	$190.0501	$190.05	$190.05	$190.10
Purchase #3	$223.87	5.441%	$236.0508	$236.05	$236.05	$236.10
Purchase #4	$242.38	5.341%	$255.3255	$255.33	$255.35	$255.30
Purchase #5	$11.76	12.684%	$13.2516	$13.25	$13.25	$13.30
Purchase #6	$91.94	6.361%	$97.7883	$97.79	$97.80	$97.80
Purchase #7	$211.53	13.617%	$240.334	$240.33	$240.35	$240.30
7 purchase totals =	$1,003.09		$1,075.4837	$1,075.48	$1,075.55	$1,075.60