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	$29.81	12.145%	$33.4304	$33.43	$33.45	$33.40
Purchase #2	$250.69	6.406%	$266.7492	$266.75	$266.75	$266.70
Purchase #3	$28.82	3.791%	$29.9126	$29.91	$29.90	$29.90
Purchase #4	$217.40	4.718%	$227.6569	$227.66	$227.65	$227.70
Purchase #5	$219.81	10.497%	$242.8835	$242.88	$242.90	$242.90
Purchase #6	$178.90	7.570%	$192.4427	$192.44	$192.45	$192.40
Purchase #7	$38.98	11.501%	$43.4631	$43.46	$43.45	$43.50
7 purchase totals =	$964.41		$1,036.5384	$1,036.53	$1,036.55	$1,036.50