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	$12.75	9.264%	$13.9312	$13.93	$13.95	$13.90
Purchase #2	$57.95	6.774%	$61.8755	$61.88	$61.90	$61.90
Purchase #3	$40.70	12.359%	$45.7301	$45.73	$45.75	$45.70
Purchase #4	$175.97	13.555%	$199.8227	$199.82	$199.80	$199.80
Purchase #5	$35.92	11.371%	$40.0045	$40.00	$40.00	$40.00
Purchase #6	$151.75	5.834%	$160.6031	$160.60	$160.60	$160.60
Purchase #7	$223.81	4.475%	$233.8255	$233.83	$233.85	$233.80
7 purchase totals =	$698.85		$755.7926	$755.79	$755.85	$755.70