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	$208.39	6.649%	$222.2459	$222.25	$222.25	$222.20
Purchase #2	$71.43	5.475%	$75.3408	$75.34	$75.35	$75.30
Purchase #3	$47.36	9.586%	$51.8999	$51.90	$51.90	$51.90
Purchase #4	$122.34	12.307%	$137.3964	$137.40	$137.40	$137.40
Purchase #5	$38.84	11.511%	$43.3109	$43.31	$43.30	$43.30
Purchase #6	$227.94	6.296%	$242.2911	$242.29	$242.30	$242.30
Purchase #7	$241.47	11.253%	$268.6426	$268.64	$268.65	$268.60
7 purchase totals =	$957.77		$1,041.1276	$1,041.13	$1,041.15	$1,041.00