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	$226.77	11.697%	$253.2953	$253.30	$253.30	$253.30
Purchase #2	$38.87	12.735%	$43.8201	$43.82	$43.80	$43.80
Purchase #3	$152.80	12.489%	$171.8832	$171.88	$171.90	$171.90
Purchase #4	$174.34	10.658%	$192.9212	$192.92	$192.90	$192.90
Purchase #5	$214.72	5.633%	$226.8152	$226.82	$226.80	$226.80
Purchase #6	$191.80	13.400%	$217.5012	$217.50	$217.50	$217.50
Purchase #7	$155.29	4.641%	$162.497	$162.50	$162.50	$162.50
7 purchase totals =	$1,154.59		$1,268.7332	$1,268.74	$1,268.70	$1,268.70