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	$142.49	9.197%	$155.5948	$155.59	$155.60	$155.60
Purchase #2	$125.87	3.767%	$130.6115	$130.61	$130.60	$130.60
Purchase #3	$230.43	12.175%	$258.4849	$258.48	$258.50	$258.50
Purchase #4	$83.49	13.247%	$94.5499	$94.55	$94.55	$94.50
Purchase #5	$153.49	13.728%	$174.5611	$174.56	$174.55	$174.60
Purchase #6	$187.86	11.212%	$208.9229	$208.92	$208.90	$208.90
Purchase #7	$100.51	8.601%	$109.1549	$109.15	$109.15	$109.20
7 purchase totals =	$1,024.14		$1,131.8800	$1,131.86	$1,131.85	$1,131.90