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	$207.72	3.689%	$215.3828	$215.38	$215.40	$215.40
Purchase #2	$164.77	12.304%	$185.0433	$185.04	$185.05	$185.00
Purchase #3	$151.70	4.545%	$158.5948	$158.59	$158.60	$158.60
Purchase #4	$84.52	4.851%	$88.6201	$88.62	$88.60	$88.60
Purchase #5	$18.94	4.507%	$19.7936	$19.79	$19.80	$19.80
Purchase #6	$26.43	5.279%	$27.8252	$27.83	$27.85	$27.80
Purchase #7	$169.82	6.183%	$180.32	$180.32	$180.30	$180.30
7 purchase totals =	$823.90		$875.5798	$875.57	$875.60	$875.50