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	$243.88	13.803%	$277.5428	$277.54	$277.55	$277.50
Purchase #2	$89.33	12.296%	$100.314	$100.31	$100.30	$100.30
Purchase #3	$200.93	13.196%	$227.4447	$227.44	$227.45	$227.40
Purchase #4	$245.90	6.397%	$261.6302	$261.63	$261.65	$261.60
Purchase #5	$13.92	9.404%	$15.229	$15.23	$15.25	$15.20
Purchase #6	$96.78	11.506%	$107.9155	$107.92	$107.90	$107.90
Purchase #7	$43.69	8.601%	$47.4478	$47.45	$47.45	$47.40
7 purchase totals =	$934.43		$1,037.5240	$1,037.52	$1,037.55	$1,037.30