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	$40.92	11.190%	$45.4989	$45.50	$45.50	$45.50
Purchase #2	$158.49	10.445%	$175.0443	$175.04	$175.05	$175.00
Purchase #3	$194.32	7.147%	$208.2081	$208.21	$208.20	$208.20
Purchase #4	$102.92	6.704%	$109.8198	$109.82	$109.80	$109.80
Purchase #5	$191.99	12.348%	$215.6969	$215.70	$215.70	$215.70
Purchase #6	$186.88	11.427%	$208.2348	$208.23	$208.25	$208.20
Purchase #7	$227.83	11.532%	$254.1034	$254.10	$254.10	$254.10
7 purchase totals =	$1,103.35		$1,216.6062	$1,216.60	$1,216.60	$1,216.50