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	$238.80	7.340%	$256.3279	$256.33	$256.35	$256.30
Purchase #2	$232.59	4.485%	$243.0217	$243.02	$243.00	$243.00
Purchase #3	$118.34	11.296%	$131.7077	$131.71	$131.70	$131.70
Purchase #4	$51.60	3.470%	$53.3905	$53.39	$53.40	$53.40
Purchase #5	$249.90	6.103%	$265.1514	$265.15	$265.15	$265.20
Purchase #6	$245.70	6.328%	$261.2479	$261.25	$261.25	$261.20
Purchase #7	$38.81	9.309%	$42.4228	$42.42	$42.40	$42.40
7 purchase totals =	$1,175.74		$1,253.2699	$1,253.27	$1,253.25	$1,253.20