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	$79.77	13.359%	$90.4265	$90.43	$90.45	$90.40
Purchase #2	$231.89	9.271%	$253.3885	$253.39	$253.40	$253.40
Purchase #3	$100.79	10.501%	$111.374	$111.37	$111.35	$111.40
Purchase #4	$116.33	3.630%	$120.5528	$120.55	$120.55	$120.60
Purchase #5	$154.49	6.289%	$164.2059	$164.21	$164.20	$164.20
Purchase #6	$213.56	12.505%	$240.2657	$240.27	$240.25	$240.30
Purchase #7	$127.57	12.643%	$143.6987	$143.70	$143.70	$143.70
7 purchase totals =	$1,024.40		$1,123.9121	$1,123.92	$1,123.90	$1,124.00