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	$221.74	13.421%	$251.4997	$251.50	$251.50	$251.50
Purchase #2	$22.43	9.245%	$24.5037	$24.50	$24.50	$24.50
Purchase #3	$39.35	3.650%	$40.7863	$40.79	$40.80	$40.80
Purchase #4	$245.47	6.548%	$261.5434	$261.54	$261.55	$261.50
Purchase #5	$103.64	9.333%	$113.3127	$113.31	$113.30	$113.30
Purchase #6	$205.82	13.436%	$233.474	$233.47	$233.45	$233.50
Purchase #7	$226.52	5.476%	$238.9242	$238.92	$238.90	$238.90
7 purchase totals =	$1,064.97		$1,164.0440	$1,164.03	$1,164.00	$1,164.00