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	$198.93	12.824%	$224.4408	$224.44	$224.45	$224.40
Purchase #2	$83.28	9.143%	$90.8943	$90.89	$90.90	$90.90
Purchase #3	$171.35	4.704%	$179.4103	$179.41	$179.40	$179.40
Purchase #4	$166.84	3.874%	$173.3034	$173.30	$173.30	$173.30
Purchase #5	$67.89	6.582%	$72.3585	$72.36	$72.35	$72.40
Purchase #6	$194.41	3.589%	$201.3874	$201.39	$201.40	$201.40
Purchase #7	$49.86	13.816%	$56.7487	$56.75	$56.75	$56.70
7 purchase totals =	$932.56		$998.5434	$998.54	$998.55	$998.50