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	$155.71	13.241%	$176.3276	$176.33	$176.35	$176.30
Purchase #2	$105.47	3.299%	$108.9495	$108.95	$108.95	$108.90
Purchase #3	$106.61	13.289%	$120.7774	$120.78	$120.80	$120.80
Purchase #4	$197.91	3.816%	$205.4622	$205.46	$205.45	$205.50
Purchase #5	$158.78	3.331%	$164.069	$164.07	$164.05	$164.10
Purchase #6	$174.74	9.438%	$191.232	$191.23	$191.25	$191.20
Purchase #7	$138.90	12.676%	$156.507	$156.51	$156.50	$156.50
7 purchase totals =	$1,038.12		$1,123.3247	$1,123.33	$1,123.35	$1,123.30